Zombie Trap

A zombie trap is a pit that zombies can jump in but cannot jump out. Be warned, this trap utilizes a bug in the zombie AI.

The Trap is created by digging a 7 block wide by 6 block deep pit, on each side of the pit you should dig out the fifth block up, leaving 1 block overhanging. Zombies will jump in, and then repeatedly jump until they turn around, but the other side is the same way and they cannot escape.

Example