Jim Wagner
You’re out hiking on an isolated trail somewhere in the backwoods enjoying nature, when suddenly you see in the distance, heading your way, three rough looking men toting assault rifles and hand radios. Fortunately, you spotted them before you they saw you, and with your quick reaction, you make your getaway onto a small side trail that’s off to your right. You’re thinking, “Surely, they won’t see me in there if I go in far enough and hide.”

About ten paces later your left shin pushes against a taunt string of some sort, and you hear a CLICK! It’s followed by the sound of breaking twigs and the rustling of a lot of leaves. From above a large log with spikes protruding out from it on all sides, swings down in an inverted arc due to the rope it is suspended by. The heavy log slams into your body like a football player you’re not ready for. Everything goes black for a moment, and at the first thing moment of consciousness you realize that you can’t breathe. Worse, you see that your body is punctured in a few places like a pin cushion, two right through the chest, and you’re stuck to this primitive weapon. You know without doubt, “This is it.”

You had just inadvertently set off a booby trap that was placed there to keep trespassers out of a secret drug growing or making operation. There were no warning signs and no indication of illegal activity. You were just in the wrong place at the wrong time, and you were totally unprepared for this kind of martial arts fight. Yes, this is a martial arts situation. What’s the literal translation of “martial arts?” It’s “war arts,” and this is just one more possible “war” that you, or someone you care about, may face one day.

The example I gave you was a mechanical booby trap, the swinging log with spikes protruding out from it, but in another reality the trip wire could be one that pulls the pin from a concealed hand grenade that reduces you to just body parts, or it could activate a chemical weapon, or even set you ablaze like a torch if it’s attached to an incendiary device. For some fighters this is very much the reality they could face: a SWAT team executing a high risk warrant on a terrorist “safe house,” soldiers on patrol in a conflict zone, or even an ex-boyfriend who wants to get even.

If you suspect that you’re in an environment where you could end up running into a trip wire, which is often a product called “invisible thread for sewing,” then chances are you won’t see it. It’s not that the thread is actually invisible, but it’s so thin and transparent, along with being strung out at ankle to knee level making it even more difficult to detect, that you won’t see it. Plus, trip wires are almost always set up at the mouth of a fatal funnel. In other words, the environment selected is ideal for naturally funneling the victim into a narrow path where tripping the device is inevitable. To make the deception work, one end of the wire must be secured to an immovable object (a tree, wall, piece of furniture, etc.) and the other end is attached to the activator (a grenade ring, a lever, switch, etc.).

If you suspect that you’re about to enter a fatal funnel that could be booby trapped, then there are two methods I know of, and I have taught them to law enforcement agencies, military units, and security teams worldwide, and I’ll share them with you. Method one is using “party string,” and method two is using “typewriter ribbon.” I’ll explain.

Party string, also known as aerosol string, is a toy that shoots out a continuous colored plastic string that’s propelled by an aerosol can. It also happens to be an excellent trip wire detector.

Before entering the fatal funnel (the beginning of a trail, a room, between large debris, etc.) you need to STOP. LOOK. AIM. PRESS. DETECT.

STOP at the first indication that you could be walking into a fatal funnel. LOOK at the direction of travel you intend to go, and scan side to side for likely places to conceal a trip wire and a trap. AIM the nozzle in the exact direction you are planning to walk, but slightly upward to arc the steam of liquid that immediately evaporates in mid-air creating the plastic string. PRESS the actuator for a few seconds to make sure that a long strand comes out of the nozzle to get the maximum effective range. Of course, you’ll only know it’s capability through practice. DETECT the trip wire, if there is one.

The string that is ejected will float down to the ground, and when it lands on the trip wire it will make a “tent.” The wire is the “support beam” with the party string hanging down on opposite ends. The material is so light that it will not pull down the string down, therefore not activating the trap. The trip wire is detected by this sign, and the area can be avoided or marked.

Silly String self defense

Jim Wagner

The same party string used for celebrations is the same substance used to detect a trip wire that is attached to a booby trap.

Silly String self defense

Jim Wagner

When the plastic string floats down to the ground it will form a “tent” if it lands on a trip wire, thus making it detectable.


Jim Wagner

Once the device is found the area can be avoided or marked to go over or around.

grenade defense

Jim Wagner

Even civilian martial arts instructors can teach their students a lesson about trip wires, the “hard way,” by using a co2 or spring powered grenade.

Although party string is effective in identifying trip wires, there are some negative aspects to this product:

1. The range of the sting burst is limited to the maximum range of approximately 10 to 20 feet, depending upon the manufacturer.

2. The nozzle can get clogged after a few uses.

3. Having a few cans of party spray can be bulky, and not practical for some environments.

The second method for detecting a trip wire is one that I learned while I was teaching my Knife Survival and Ground Survival courses to recruits of the Israel Defense Forces at military base Bahad 8 in December 2003. More specifically, it was my host, Major Avi Nardia, who is now world renowned for introducing the KAPAP system outside of Israel due to my insistence and persistence, and that is using typewriter ribbon.

The old mechanical typewriters, and some of the older electrical typewriters, use typewriter ribbon to get the ink onto the paper by having the letter keys strike it. The ribbon has two spools. One spool feeds the ribbon across the key striking area, and the other spool receives the used portion of the ribbon. The way to find a trip wire, using typewriter ribbon, is to hold a full spool in the throwing hand, while hanging onto the receiving spool, the “tail,” in the other hand, then lobbing the full spool over the target area as far as it will fly. During flight the spool will unravel, and then the ribbon will gently float to the ground. Like the party string, the ribbon that falls on the trip wire will make a “tent.”

The drawback to typewriter ribbon is that it’s expensive since they are for antiques. On the other hand, if you have some old music cassette tapes laying around, or you come across some old VHS video cassette tapes that someone is getting rid of at a garage sale, you can break open the plastic cover and salvage the magnetic tape that’s inside. The magnetic tape will function exactly like the typewriter ribbon.

The good thing about magnetic tape taken from music cassettes is that several of them can easily fit into a pocket. This is perfect for clearing a multi-room building. The VHS video cassette tape spool is larger, which means that you can throw it farther due to the weight. This would be ideal if you are entering a warehouse or the trail you suspect of being booby trapped.

This knowledge is not for everyone’s reality, but if it is, you now have two ways to detect a trip wire.


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