Punji stick

The presence of punji sticks may be camouflaged by natural undergrowth, crops, grass, brush or similar materials.

They were often incorporated into various types of traps; for example, a camouflaged pit into which a soldier might fall (it would then be a trou de loup).

Such pits would require time and care to dig the soldier's leg out, immobilizing the unit longer than if the foot were simply pierced, in which case the victim could be evacuated by stretcher or fireman's carry if necessary.

Punji sticks were not necessarily meant to kill the person who stepped on them; rather, they were sometimes designed specifically to only wound the enemy and slow or halt their unit while the victim was evacuated to a medical facility.

[1] In the Vietnam War, this method was used to force wounded soldiers to be transported by helicopter to a medical hospital for treatment.