This is the spike pit. It was generally hidden with leaves or sticks on top so no one would know it was there. The trap was usually put where someone would land with a lot of force such as a landing zone. So that when people jumped out of the helicopter they would land harshly on the spikes.
This is the gate trap. This consisted of a grenade set beneath a gate so that when a soldier went to open the gate the grenade would explode under the soldiers feet.
This is a angled arrow trap. The arrow laid slanted up so that when someone would trip the trip wire the arrow would shoot right into them.
Toe poppers were generally put in areas with tall grass which made them hard to see. The toe popper was a bullet or artillery shell that barely stuck out of the ground. Once someone stepped on this trap it would most likely blow your foot off.
The door trap was a piece of bamboo with spikes in it hanging above a door so when someone went in the door or opened the door it would swing down and stab them.
The whip trap is activated by a trip wire. When the trip wire is activated the bamboo with a spike on the end will swing into the person who tripped the wire.
The grenade trap is activated by a trip wire. One end of the trip wire is attached to a grenade pin so when the trip wire is moved the pin will be pulled and the grenade will explode.
The spike board is like a teeter totter when one end is pushed down the other end flies up. So when someone steps on the trap the other end of the board filled with spikes will fly into them.
Booby trap markers were commonly used so that the Vietcong could make sure they would not fall into their own trap.
Links used for this information. http://www.5rar.asn.au/weapons/boobytraps.htm
http://vietnam-warfare.tripod.com/vietnamwarfare/id3.html
http://vietnam-warfare.tripod.com/vietnamwarfare/id3.html