This glitch allows you to jump on a table in Zombie Mode where the zombies cannot touch you. This glitch has been patched so you will need to remove the update and play offline. However PLEASE NOTE - you cannot remove the patch conventionally as other patches via clearing the System Cache.
You need to PRESS the Xbox 360 Guide Button > Settings > System Settings > Memory > Pick a Save Location eg Hard Drive > Games
Scroll down to Call Of Duty Black Ops and delete the Update. There's no need to delete the saved game.
PLEASE NOTE deleting Updates can affect game data. You do so at your own risk.
Credit goes to MMMMMMMMMMMMMEH for the information on deleting game updates.
Glitches That Unlock Achievements 