"Well, basic traps that don't include flying spikes and Giant boulders crushing anything in its path are Bear Traps! It could easily cut of flesh/leg of an Infected. Bear traps can also prevent the Infected from moving anywhere away/ out of the trap."

"I have a couple of large antique bear traps and they would certainly hold a person that stepped in them.
Downside is that they are far from common and usually are pretty expensive, even a repo one [whose springs may not be properly tempered] will set you back around $300-$400
They are also very heavy and can be extreamly hard to set. I set one of mine befor using large c clamps and was not easy

A better solution would be snares or set guns...old shotgun attached to a tree with a trip wire going to the trigger.
Few months ago I bought an original antique 20 ga.set gun that is mounted on a tripod and can be aimed. It is set off by pulling a string. Guns like this were used to shoot bears, wolves etc. as well as being set in buildings to harvest burglers..."

"i would sway away from bear traps theyre very exspensive and hard to set try somthing smaller like a hog trap same concept as a bear trap but less strong and slightly smaller"

"
With all that said, even the lethal traps could also be camouflaged, as long as they are of the "command detonated" sort that can only be set off by some deliberate action on the part of the defenders. For example, the military uses landmines that are detonated by remote control when an enemy is observed walking into the target area. As remote fired land mines probably won't be available, the same thing might be accomplished by a spear trap or deadfall that is set off not by an enemy hitting a trip wire, but by a defender (perhaps hidden in the bushes nearby) pulling a string or whatever. "

"Now the next step in this train-of-thought is to think about Zombie behaviour, how it's different from humans and how to take advantage of it. unfortunately they don't exist, But I think this is a key idea in bridging the gap between the basic function/necessities of traps, and rebuttals like pedros'. Taking advantage of idiosyncratic behaviour in the target, and designing the trap based on that to target them and no-one else. "