Noclip

Noclip, also known as fly and ghost, is a cheat that disables the effect of gravity and makes all objects nonsolid to the player. This allows you to glide freely through the world. If you exit the world or simply fly into a wall you will be unable to shoot.

Warning:If you try to noclip your way too far out of the map (out of Hammer workspace) the game will crash. This will also occur if the sv_noclipspeed is set too high.