A boobytrap is any form of concealed mechanism that is placed in such a manner that it will be set off inadvertently by the enemy or function by means of a delay mechanism. They are designed to destroy personnel, vehicles, equipment, or communications. Normally an explosive charge is employed that is fired by a mechanism but it may make use of incendiary devices as well. Boobytraps are designed to create an atmosphere of uncertainty and impose caution on the enemy and so lower morale and slowing him down. The casualties and damage are merely a means to that end.
Prior to the Second World War, I am not aware of any devices developed specifically for the purpose of boobytrapping. There were undoubtedly nasty surprises left behind by withdrawing troops in the trenches of the First World War, but they would have fallen into the improvised boobytrap class.
Boobytrap mechanisms are normally operated by the following methods:
Pressure- Direct pressure by the foot, wheel, or track on the mechanism.
Release- By the removal of a weight on the top of the mechanism.
Pull- By moving some object that is attached to the mechanism or tripping a trip wire.
Delay- By means of a clockwork mechanism or some other form of delay device.