From The American Thinker:
There are varieties of the monkey trap used in Africa, South America and Asia. Some are pottery jugs, some are wooden boxes, but all work on the same principle. The trap is secured to something, perhaps tied to a tree. There is an opening in the trap large enough for the target monkey to reach his hand inside. Bait, usually nuts, is placed in the trap. The monkey reaches in, grasps a fistful of nuts, and finds that when his hand is clenched around the bait, he can’t remove it from the trap.