Wall hacking

Wall Hacking is the use of glitches in the Halo and Halo 2 physics engines that allows players and objects to go through walls and barriers, usually to cheat.

One common and well-known example of this is on the Multiplayer map Danger Canyon on Halo: Combat Evolved. Because this map is arranged in a circle, with the two bases next to each other (albeit with a wall in between), if you flew through the wall, you would get to the opposing team's base. People have done this in Team CTF games when Team Kill / Friendly Fire is turned off in the game settings, 'ramming' another teammate through the wall with a high-speed land vehicle like a Ghost or a Warthog, and the 'rammed' player breaking through the walls to the other side. Sometimes the player does not have enough velocity to travel through both walls, they will fall through the map and die.

In Halo 2, certain maps have certain spots where, if you are thrown with enough force at a certain angle or speed, you will fall through the map. This usually only happens with ragdoll animations, used when a player is killed.