Estimated reading time: 28 minutes
A lot of folks have never put together a trip wire alarm, and there’s a good reason. There are just not a lot of occasions where a trip wire is necessary. However, when those occasions do emerge, it’s at least worth understanding the concept of what works and what doesn’t.
What Exactly is a Trip Wire?
A trip wire is a long length of thin wire, monofilament fishing line, or any other type of cordage that is usually connected to something that makes noise. The idea is that when an intruder either human or animal steps into the wire, the alarm is sprung, alerting you to an intrusion.
The trip wire concept was developed in wartime as a way to alert troops of an enemy incursion. This was particularly needed at night and was often used in the dense island jungles during the war in the Pacific in World War II.
The usual configuration was a thin length of rope suspended low to the ground between trees with empty C-ration cans filled with stones to rattle the alarm whenever the wire was “tripped.” And while booby traps were sometimes used to maim or kill, there was always the concern that an innocent civilian or friendly soldier wandering off to go relieve himself would trip the wire.
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But Who Needs Them Now?
The usual reason someone considers a trip wire is when they are in an area with the potential for any number of unknown threats. The idea is usually to make noise to signal an intruder.
- The threat could be from wild animals like bears or wolves approaching a camp in a remote area.
- In countries ravaged by civil wars and civil unrest, no night is safe and trip wires are sometimes used to at least alert the local population if a covert threat is approaching.
- Following a disaster, many people find themselves isolated and alone with the potential for looters or worse. That’s when a trip wire may at least scare them off, if not serve as a warning of an unwelcome approach.
- In times requiring a bug-out to a distant but safer location, there are occasions where a night must be spent on the road in unknown territory where the threat is equally mysterious. Trip wires would serve as a perimeter defense to at least alert anyone spending an unplanned night on the road of any approach.
- And yes, they’re still used in war zones, although the technology of trip wires in those areas is usually defined by lasers, electronic signals, or infrared beams connected to electronic alerts through cameras or video or in extreme cases: explosives.
- In fact, the concept of contemporary home security systems connected to motion-detector technology to turn on lights; sound an alarm, record video, or alert the local police are the 21st century versions of the trip wire concept.
Do It Yourself Versus Buy It Yourself
It may seem unnecessary to build your own trip wires when so many options appear on the Internet, but if a situation makes the Internet undependable or unavailable, or deliveries or the purchase of many things is difficult or impossible, that might be a good time to know how to improvise a trip wire.
There’s also the fact that in some instances, the electricity is out or unavailable, and most modern security solutions require at least some level of power. In a worst case scenario with a total grid failure, technology will quickly diminish and old-school, analog solutions will offer the most dependable options. Those are the types of trip wire concepts we’ll cover.
Trip Wire 101
We might as well start with the wire. There are a variety of options. Usually, the wire or cord is low-profile and hard to see. It also needs to be relatively strong. If someone or something walks through the wire or cord and it easily breaks, little is accomplished except alerting the intruder to the fact that you’ve setup some trip wires.
Here are options to consider:
Electrical wire comes in a variety of gauges, but the smallest (and most inexpensive) gauges are referred to as 14 and 16 gauge. They’re more than strong enough to serve as a trip wire.
They’re all coated with a flexible plastic coating that comes in a range of colors. White, black, red, and green are the most common, and those colors present camouflaged, stealth characteristics, depending on the time of year, time of day, and natural surroundings. Floral wire is another option and also comes in a variety of colors.
Monofilament Fishing Line
Fishing line is thin, strong, and also hard to see. Buy one of the heavier weight tests of at least 50 pounds or more. Avoid any of the brightly colored lines. Go with a neutral, plain monofilament.
Paracord is another surprisingly strong option, but you have to think about the color of the cord. During winter, a white Paracord might makes sense if the ground is snow covered. A green or camo cord could work well in a forest or field. Black is an obvious choice for night.
You don’t see bungee cord mentioned in a lot of the write-ups about trip wires, but it has a characteristic that could make sense if you think about it. If the idea of your trip wire is to rattle a bell, cans, or other noise maker, a bungee cord will certainly make that happen.
In fact, a bungee cord may cause more noise to occur than any of the other options we’ve mentioned due to its flexibility and springiness. A black bungee makes sense. Green if you’re in the woods.
If your trip wire is designed to trigger a mechanism, bungee is not the best choice, but if you’re rattling cans the old-fashioned way, it’s a good option.
Lasers, Infrared, and Motion Detectors
You can buy these things and improvise a trip wire yourself, but make sure they’re battery or solar powered or have a way to recharge the batteries. These are complicated solutions, so we’ll mention them but we’re not going to spend a lot of time covering ways to make technology work in a primitive environment.
Some websites offer tips and solutions to improvising trip wires with technology, but it’s a lot of work and you have to consider how and when you’ll need any trip wire, and for how long.
The idea of most trip wires is to make a lot of noise when someone trips over the wire. Noise makers vary depending on what you have available or may have bought in advance. We’re going to assume your situation caught you a bit by surprise and that you have to improvise from available materials.
It’s believable that a lot of us would have wire, cords, and fishing line lying, around but things that make noise require a bit of creativity or at least some pre-planning, especially if you require a very loud alarm.
How loud your alarm needs to be depends on your distance from the trip wire and whether you are inside or outside. Someone camping in a tent will be more likely to hear a rattle of rocks in a can than someone sleeping in their home or cabin.
If you are at a distance from your trip wire or indoors, you may need to plan and buy ahead to acquire louder alarms like blank cartridge firing mechanisms, firecracker poppers, air horns, or anything else that will be heard under most circumstances.
And if you can, paint your alarms to match the environment. If you don’t have paint, you can rub some mud or clay on the bell/can/noisemaker so it is somewhat camouflaged. Black is good at night, camo combos for any natural forest or field, and snow white for winter.
If you’re trying to keep animals at bay, the colors are less of an issue. Animals only see in black and white, but keep an eye on the contrast. They can still notice highly contrasting shades.
A lot of us have bells around for various reasons including cowbells, Christmas bells, antique bells, and collectible bells. And then some of us don’t. If you have any assortment of bells, you’re off to a good start with a trip wire.
Rocks in Cans
Even if you’re not a bell collector, there’s a good chance you have access to tin cans and rocks. No rocks? Anything that makes noise in a can will do from bolts to nuts or better yet, marbles— although marbles may jostle around in your can in the wind, so maybe stick with the pebbles.
You only want a few in the can but enough to make noise when the can is jostled. Smooth, rounded stones and marbles are best. Look for rounded stones in river and creek beds.
Drop a few in and give the can a shake. Adjust until you think you have the most and best noise for a shake. And if you don’t think a rattling can is going to work, then you’ll need to think about stocking some very loud alarms like the next few items.
There’s a type of firework that has two stings emerging from either end of a firecracker. When you pull the stings, the firecracker pops. They’re loud, and you can tie them onto a number of trip wires around your area.
Some of them are made out of paper and will get wet due to rain, snow, or morning dew, so wrap them in plastic cut from a black or neutral garbage bag. They’ll most likely scare off a wild animal and might scare off an intruder. Either way you’ll certainly hear it.
This isn’t about setting up a full loaded .22 caliber round on a trip wire. That’s a really bad idea. Trip wires are indiscriminate and when tripped, the wire fires. Most .22-caliber blanks are used for nail hammers to drive nails and pins into concrete.
The firing mechanism for trip wires and .22 blanks can be bought online, although the blanks are available at most hardware stores next to the nail guns. There are also 12-gauge blank variations on this concept.
As a trip wire, they’re mostly designed to deter wild animals, but the people who sell them offer all sorts of reasons to use them. You’ll certainly hear it, and it will scare most anyone and anything away.
However, it may cause a response you don’t necessarily want. If someone is approaching and they are armed, they may perceive the detonation of a .22-caliber blank round as actual gunfire and return fire. Up to you.
Air Horns, Sirens, and Other Noise Makers
If it makes noise, it’ll work on a trip wire. The only challenge is figuring out how to trigger the noise. Things like sirens need power, but if you’re handy with a little wiring, you can make a trip-switch to set off the siren.
There are also solar powered options available. There’s some advice out there about setting up a rock over an air horn that will fall on the air horn button when tripped. That requires some precise setup and once that rock is on the air horn, it’s going to make a lot of noise until you lift the rock.
You’ll also probably use up all the air in the horn by the time you get out of bed or your sleeping bag to lift the rock.
What About Light?
There are solar powered motion detectors that will illuminate an area. These are best hung high in a tree out of sight and out of reach. It’s a variation on the trip wire concept, and it’s usually used to dissuade animals. It could also deter an intruder, but if you’re using something to trip an alarm that will notify you of an intrusion, a light in the night will do little good if you don’t see it while you’re sleeping or otherwise occupied.
Most trip wire concepts are designed to make noise to let you know that someone or something is approaching, and improvising a light to a trip wire can get a little complicated unless you have some good skills with wiring and trip switches. We’re going to skip the lights and stick with noise.
This Is NOT About the Use of Lethal Force
Booby traps have often been used in times of war and they are designed to kill. That’s a really bad idea. The whole idea is to either scare something or someone away with sound or to at least be alerted to the presence of something approaching.
Even a blank .22-caliber cartridge should be pointed towards the ground. Otherwise, the blast could send shrapnel from a tree trunk or branch in someone’s direction, and you don’t want it to be one of your children or an innocent wanderer lost in the night. This is about making noise, not war.
Location, Location, Location
Where you place any trip wire is as important as the design of the trip wire itself. You want it far enough away to give yourself some time to observe the direction of the alarm and see what’s coming plus prepare to respond. But you also want it close enough so you can hear it.
Another location factor is the height of the trip wire from the ground. If you’re concerned about human intruders or large animals like a bear, you’ll want your trip wire about a foot above the ground. 6-inches above the ground is about the minimum or someone or something could step on the wire without tripping it.
Also, if it’s any lower than 6 inches, every random squirrel, raccoon, possum or most any other rodent could trip your wire repeatedly. If that happens enough, you may take to ignoring the trip wire noise while assuming it’s just another passing rabbit when it’s the intruder you were so worried about in the first place.
Support for attaching a trip wire is something else to think about. A lot depends on what’s available at the location and what kind of trip wire you’re using. Two tree trunks could work, but they will create a very taut trip wire that may not ring any bells for long. They could also cause an intruder to literally trip which may be an effective deterrent–or not.
The branches of two trees or two saplings give some flexibility to any trip wire and could result in a sway in the wire, causing the noise to persist a little longer.
Two stakes in the ground are another solution, but if you’re trying to raise your trip wire to a foot of height, you’ll need long and large stakes deeply imbedded in the ground.
The number of trip wires you set up is another location consideration. Think in terms of avenues of approach. Around a home or dwelling, any open area like a gap in a fence, a gate, an open back or front yard, approaches to doors or windows, or approaches to outbuildings are worth thinking about.
A lot depends on what you’re worried about, the location, and the immediate threat level.
A remote survival camp or any campsite for that matter might require a number of trip wire setups, but even then –animals prefer open paths and clear terrain. A human intruder may do otherwise and stick to the cover of scrub, brush, and trees, so you just have to do your best to estimate what could be coming and from where.
Check your trip wires if you have them in place for any length of time. Improvising an alarm with some rocks in a can is a good idea, at least until it rains or freezes and the water or frozen rocks in the can fail to rattle.
It’s also possible one of your trips has worked loose; been tripped without you knowing it, and loose on the ground, or something as simple as a knot that has worked loose. It’s actually somewhat of a “set it and forget it” approach, but it’s worth checking them from time to time if you need them for any duration.
Remove your trip wires when you don’t need them anymore or when you move on. They will cause you or anyone else to trip, including family members, as long as they’re in place. You also may need them again.
The DIY Trip wires
1. Bungee Marbles
The advantage of a bungee cord as a trip wire is its springiness. Think of it as a rubber band on steroids. In fact, the interior of a bungee cord is just that. Long strands of rubber encased in a flexible fabric braid.
You can attach anything that makes noise to a bungee cord. The advantage is that a bungee will rattle and shake longer while making more noise.
- Bungee cord of sufficient length for your trip wire area. You can buy coiled bungee cord in various colors and cut them to length. If you only have packaged bungee cords of varying lengths with hooks, you can connect them together, although the hooks will be somewhat visible during the day.
- Various soup cans painted to match the terrain or time of day. They should also have holes punched towards the top of the can on either side.
- (You can substitute bells for the cans.)
- Choose a bungee cord color that you think will blend in the best with the surrounding areas.
- Wrap the one end of the bungee around a tree trunk, branch, sapling or stake. Tie it off with two half-hitches and pull tight.
- Thread your can or cans onto the bungee.
- Stretch it tight to another tree trunk, branch, sapling or stake and wrap and knot with two half hitches until tightened.
- Add marbles to the can and test it with a few pulls on the bungee. Add or remove marbles depending on the sound.
- Test your bungee trip wire again with someone in camp or in the house and ask them if they can hear the cans? If not, move the trip wire closer or add some more cans.
2. Monofilament on the Rocks
Monofilament is an excellent trip wire source. It’s hard to see during the day and totally invisible at night. The key is to have a strong enough weight test to activate the noise without breaking. It can be used in most any trip wire setup in any location.
- Monofilament fishing line. 50 pound test or higher is best, but any weight test will do if it’s all you have on hand. You could even double or triple up the monofilament if you’re worried it will break or snap.
- Empty tin cans. Soup cans are a good size. Peel off any colorful labels and either paint them or coat them in a thin film of mud so they are less reflective. Paint the cans black or do a camo pattern depending on the surrounding area.
- Smooth, round rocks, nuts, bolts, marbles—anything hard that can easily move around and rattle in the can.
- Cordage or wire to attach the cans to the monofilament.
- Wrap the one end of the monofilament around a tree trunk, branch, sapling or stake. Tie it off with an improved clinch knot (a fishing knot perfectly suited to monofilament) and pull tight.
- Punch 4 holes in each can.
The holes should be punched in pairs towards the top of the can about a ½ inch apart and opposite each other at the rim of the can. This is so the can is bound tight to the monofilament as it is threaded through the holes to ensure a good shake.
- Thread the monofilament through the holes.
- Add the can or cans along the monofilament, but try to place them in spots that are obscured by brush, tall grass, or other natural camouflage. It makes no difference at night, but take a look when it’s dark to be sure.
- Stretch it tight to another tree trunk, branch, sapling, or stake and wrap and knot with another improved clinch knot and pull light.
- Try to locate the cans in a location that is hard to see during the day.
- Drop a few rocks in the can and shake the fishing line wire to see if the cans rattle. Add more or less rocks until the cans make a racket. Continue to add cans where you can. Tighten the cans to the monofilament if you need to.
- Test your monofilament trip wire and have someone in camp listen and ask them if they can hear the cans. If not, move the trip wire closer or add more cans.
3. Paracord Pull-String Fireworks
- Thin paracord. A type I or type II is thin enough to be obscure but strong enough to function as a trip wire. Choose the color that best matches the terrain and time of day.
- Pull-string fireworks. They’re legal to buy in most states and can also be purchased online. You’ll need to have them on hand because they’re very difficult to improvise.
- Choose a paracord color that will blend in with the surrounding area.
- Wrap the one end of the paracord around a tree trunk, branch, sapling, or stake.
- Find a location that is hard to see along the paracord and tie one end of the pull-string firecracker to the cord.
- Tie the other end of the paracord to another tree trunk, branch, sapling, or stake and wrap and knot with two half hitches until tightened.
- Carefully tie the paracord to the other end of the pull-string using a square knot or any knot you can improvise. You have to do this delicately. You want the paracord tight, but you don’t want to accidentally detonate the firecracker. If you want to get the best tight line, you could tie the final end of the paracord to the tree or stake with a trucker’s hitch. This will give you a little more control over the slack, but be gentle.
- You don’t want to test your popper trip wire or you’ll have to retie another one. If you want to test the distance and whether or not you’ll hear it, have someone in camp or in the house listen while you pull a spare popper. If they don’t hear it, move the trip wire closer. Don’t be tempted to add multiple poppers to the same trip wire. What will most likely happen is that one popper will trip, leaving any others unexploded.
- Unlike bells and tin cans, you have to rearm your firecracker trip wire whenever it goes off. That’s not a bad idea to at least see if there are any footprints or paw prints to tell you if your intruder was human or a stray dog.
4. Thin Wire .22-Caliber Blank
- Floral wire. Black is the default color, but if you have a green or white color that can match the terrain or time of year (snow), that’s a good idea.
- A .22-gauge firing capsule. You can buy these online. They’re hard to find in stores.
- Blank .22-gauge loads. Buy these online where you bought your firing capsule or at a hardware store in the nail bun aisle.
- Wrap the one end of the wire around a tree trunk, branch, sapling or stake. Choose a color that matches best with the surroundings.
- Attach an unloaded .22-gauge capsule in an obscure spot.
- Attach the other end of the wire to the .22-gauge firing capsule.
- Stretch it to another tree trunk, branch, sapling or stake and pull until you have tension on the .22-gauge firing mechanism.
- Test the unloaded .22-gauge capsule by pushing on the trip wire to see if the pin fires. If not, adjust the tension. If the pin fires, rearm the firing mechanism and carefully add a blank .22-gauge cartridge.
- If appropriate to the situation, do a test. It will be loud and attract a lot of attention. If the firing pin is firing when unloaded, you should be good to go if a test causes local problems or concerns. Anything that sounds like a gun shot in the neighborhood may attract some unwanted attention.
5. Winter White Trip Wire
This setup uses a white length of electrical wire attached with overlapping loops through two holes in the top of a can painted white. Obviously, it’s a winter trip wire and it uses marbles or pebbles to create the alarm. The overlap of the wires causes the can to shake and rattle more than a conventional wire or line passing through the holes.
- White electrical wire
- A can or cans painted white
- Marbles or pebbles
- Attach one end of the wire to a tree branch.
- Run the wire through the can in a discreet location, but overlap the wires so the can shakes when the wire is tripped.
- Attach the other end of the wire to a branch and test.
6. Back Gate Avalanche
If trouble is close to home and you need to come up with a trip wire fast, this is one option. This is a trip wire connected to a gate, causing an avalanche of large rocks to fall onto a large piece of sheet metal or even a metal garbage can. It makes a lot of noise and can also be staged so the rocks fall onto the metal when the gate is pushed rather than pulled open.
You can improvise this kind of setup anywhere someone may enter uninvited, from a barn door to a back door to a door on a wood shed. This is not a stealthy trip wire. It assumes that a gate or other barrier is obstructing any view of the setup.
- Bucket to hold the rocks.
- About two dozen large rocks from 1 to 2-inches in diameter.
- A large metal surface or object that will make a lot of noise when rocks land on it. Sheet metal, metal garbage cans, metal ductwork, any type of metal that’s relatively thin and will create noise.
- A wood platform 12” square to support the bucket
- Three wooden dowels about 3 feet long. (You can use old broom handles or even 1×2’s can work).
- Cordage. Any type and any color. The trip wire will also be obscured by the gate or barrier.
- Fill your bucket with your rocks and dump them on your metal sheet, can or whatever else your using to assess the noise. Ask someone inside your home or camp to determine if they can hear it.
- If you’re satisfied with the noise level, fill the bucket with your rocks.
- Pound the 3 support sticks into the ground in a triangle that will support the 12” square platform.
- Set the 12” platform on top of the support sticks. You don’t want to drive the support sticks too deep into the ground. You want this to be a precarious balancing act.
- You have two options. If your gate pulls open towards you, attach your trip wire to the gate and to the front support stick or your three sticks setup far enough away to allow the rocks to fall on the metal. Place the metal in the best location for the rocks to fall. You might want to put some rocks under the metal to lift it off the ground to increase the noise and hold it in place to some degree. When the gate is opened, the trip wire will pull out the support and the bucket will fall forward onto the metal.
- If your gate opens away from you, set up the support sticks and the platform right next to the gate. When someone pushes the gate open, it will topple the bucket with the rocks onto your metal plate or can.
- Test either option to see where the rocks fall and place your metal sheet or container in that location.
- Test again and ask someone inside the house to assess the noise level.
- If satisfied, set the trip or add more rocks or adjust the metal location or type of metal. It’s an easy set up and will create enough noise to cause most intruders to jump out of their boots.
Are There Other Approaches?
No doubt. Trip wires have been around a long time, and what you choose to improvise is only limited by your imagination and materials on hand. What we tried to do here was explore the concept so anyone could take the basic idea and adapt it to their needs, available supplies, and their location. It’s all a question of finding stuff that will make a lot of noise when someone trips over your wire.
Is this a good idea?
In an emergency, it’s good to know how to do this stuff. In an ideal scenario, you would have sophisticated electronic devices that are solar powered and connected to motion detectors and all manner of alerts and alarms. Complicating things further is that any device with any level of electronics will also need to be weatherproof.
But this isn’t about an ideal scenario with a house surrounded by lasers. It’s about a sudden and surprising time when things rapidly become dangerous or threatening. Anyone in that situation would have plenty to think about and the ability to quickly improvise something as basic as perimeter alarms with trip wires not only makes sense but simply seems like a good idea. Just don’t throw way any old bells.
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