Setting up booby traps is illegal. No matter what. When I say "known man made death traps", I mean something like the following (which is a case I actually had): A deep, but narrow trench cut on someone's land is covered by high grass that is cut at the end of the season and then the property got covered in snow, making the trench completely invisible. Man walks dog on the property (trespassing), dog got loose, while the guy was chasing the dog he fell into the trench and suffers serious injuries.

If you set up a bunch of punji traps on your property, not only are you going to get sued if someone gets injured, you're probably also going to get arrested, regardless of signage.

This all comes with the admonishment that this is not legal advice and you should not rely on it for anything except, maybe, entertainment purposes.

One of the few things that has stuck with me from law school and preparing for the bar lo these many years ago, is that there is a very low duty of care to trespassers upon your land, but there is a duty to warn of "known, man-made deathtraps", even to people on your land illegally. So, yeah, no booby-traps.