I was thinking ( dangerous for me!) about what can easily be done, to be forewarned about any "visitor's" coming into your area. 1) I had to consider the legality, that alone dispels any use of "boobytraps", as I was trained in 1969-1970. ( darn it!) 2) The ease of construction and use is very important. 3) The costs and maintenance of devices. Well, we have those crummy el-cheapo devices, touted as "driveway alarms"! ( Chinese types) that cost $15-$20. They will work, BUT they also trip many false alarms if the wind is blowing...and they have to have many batteries...3 AA's for the transmitters and 1 9 volt for the receivers. Cold and rain is NOT good for them! I threw 2 away already! They don't last long and use of more than one can be a REAL problem! They use the same frequencies and one alarm, trips 2 or more receivers! Now, an easy and cheap way is to use clothespins, some wire and either a buzzer, lights, or any electrical device ( say 9-12 volt dc) when the device is tripped to get your attention. I bought 50 clothes pins for $3.00,spray painted them, one side reddish brown to match the color of the ground up north, and the other side is juniper green, IF I choose to put them up in the existing trees. For contacts ( VERY good ones!) I soldered wires ( about a foot long) to pennies. Then I epoxied the pennies to the clothes pins, one on the top jaw, the other to the lower, and let them set in contact with each other as the epoxy cured. Once they are cured, they can be mounted in a variety of ways...( drill tiny holes in the ends and use nails or even screws for mounting, or wire to tie them up) To rocks, tree branches, or even wood stakes or even small boards. The whole idea is to place them in areas where any foot traffic will trip them. For an electrical separator, I used thin plastic strips cut from empty bleach bottles....I use a paper punch to make small holes in the ends of the strips, which are about 1/2 inch wide and 3/4 inch long. Those are also painted... You simply tie a thin wire ( I prefer 4-6lb. fishing line) into the holes and then tie it across an area where people would walk thru. The clothes pin is anchored ( one person had me epoxy his clothes pins to several meduim sized rocks ( native to the immediate area)) Then the trip line is tied off, some may be taut, while others a bit loose, and they can be varied from 1 1/2 inches off the ground to whatever height you decide to use. I like to set some around 24-30 inches! Hard to step over, and IF you are looking down at your feet, odds are you won't even see the clear monofilament! Now dogs and small critters will trip them if you put them too low ( rabbits are a nuisance! But, good eating!!!) You simply can power these by a battery ( your choice) and either have a led light ( night use) or some device such as a piezo buizzer to make an alarm. Wirng is as simple as can be. One wire goes to the (+) positive side of either the battery or the alarm device, the other wire is connected to the battery or device at the (- )negative side. All that happens is it's a small switch. The line/tripwire is pulled on, the plastic tab is 'easily' pulled out from between the 2 pennies and the contacts ( pennies) close, completing the circuitry. Simple and VERY effective! Cheap and easy! Now you can stack large rocks, cut ditches, build anti-tank traps/ditching or fall trees, such as an Abatis. But this is easy and fast! One guy is making a box with a plexiglass cover, spraying it with a special "frost" paint that is used to make bathroom windows opaque. Then wiring the thing to several of these with a switch that allows him to use either red LED's, or a piezo buzzer, and he has made a grid on the plexiglass, that shows different "zone/areas" that each alarm is located in! Only limited by your own imagination! Other devices ( but very sensitive) are the same type of simple system, using mousetraps and instead of pennies, connect one wire to the mouse trap metal wires, and the other to either a penny, or a brass or copper tack, that the "bar" contacts! They are very sensitive, and I would only use them in between trees, and at a height of around 3 to 4 feet. Your "trip wire" is tied to the bait bar on the trap and it's a bear to set up ( I hate getting my fingers snapped!) you have to use very light line and tie it LOOSELY! Wind will trip these if not protected from tree/branch movement. Now on to yet another device.... I like to use these on fences and gates, but they have to be hidden behind signs! They are simply made of pvc pipe,a cap and thin copper wire with lead sinkers. What some people may know as a "trembler". Movement sets these off fast! You have a short 4-6 inch of 1/2 or 3/4 inch diameter pvc pipe, and caps to fit. You line the inside of the pipe with aluminum foil ( glued into place),.. contact cement is good. Then you use a thin wire, with a small ( I mean tiny!) drill bit to drill a hole in the center of one pvc cap. You measure out the length of wire you'll need after wrapping it in good contact with a bass type, casting sinker ( like a bell gong!) You feed it up thru the pipe cap or feed the wire thu the whole assy just before sealing. It's easier to do with the cap off! You hot glue or affix the wire to the cap at the hole (epoxy or?) and then glue the cap to the pipe. making sure that the lead sinker inside acts as a "pendulum", contacting the aluminum foil inside the pipe. ( it must move freely and easily) When that is done you glue the lower cap on and let it dry. When you place this "trembler" on a post, fence or gate, you may have to use an ohmmeter, to enusre the "pendulum" is NOT in contact and perfectly vertical when you set it "permanently" in place. It has 2 wires, one is the pedulum wire and the other is a wire you have glued inside the pvc pipe with the aluminum foil over top of it, ensuring good conductivity. Those wires MUST be hidden and if not, they must be epoxied securely to the pipe's exterior and then painted over to camo them. They could be cut otherwise and that would nullify the system. The wiring circuitry is the same as the other 2 above. These are the same types ( not design) used in bank vaults to alarm IF anyone attempts to drill the safe or vault. They are very very sensitive and you can adjust that, simply by using different wire diameters for the pendulums. More later!