Punji stick

The Punji stick or Punji stake is a type of booby trapped stake. It is a simple spike, made out of wood or bamboo, generally placed upright in the ground. Punji sticks are usually deployed in substantial numbers.

Description
Punji sticks would be placed in areas likely to be passed through by enemy troops. 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 man might fall (it would then be a trou de loup).

Sometimes a pit would be dug with punji sticks in the sides pointing downward at an angle. A soldier stepping into the pit would find it impossible to remove his leg without doing severe damage, and injuries might be incurred by the simple act of falling forward while one's leg is in a narrow, vertical, stake-lined pit. 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 sometimes deployed in the preparation of an ambush. In the preparation of these stakes, the stake itself would be sharpened and, in some cases, rubbed with toxic plants, frogs or even feces, to cause infections in the wounded enemy. Soldiers lying in wait for the enemy to pass would deploy punji sticks in the areas where the surprised enemy might be expected to take cover, thus, soldiers diving for cover would impale themselves.

The point of penetration was usually in the foot or lower leg area. Punji sticks were not necessarily meant to kill the person who stepped on it; rather, they were designed to wound the enemy and slow or halt his unit while the victim was evacuated to a medical facility.

Vietnam War
In the Vietnam War, the Viet Cong would also use this method to force the wounded soldier to be transported by helicopter to a medical hospital for treatment, which was viewed as being more damaging to the enemy's cause than death.

Punji sticks were also used in Vietnam to complement various defenses, such as barbed wire.

Etymology
The term first appeared in the English language in 1870s, after the British Indian Army encountered the sticks in their border conflicts against the Kachins of north east Burma (and it is from their language that term is derived).