Wall running is a bug in the Quake engine that allows a player to move faster than normal. This is accomplished by standing next to a smooth wall and sprinting parallel to it. The player must then aim very slightly towards the wall and 'strafe' into it. For example, if the wall was on the right of the player, they would look slightly right and hold D to move right, while of course, holding W and Sprint. Similarly, if the wall was on the left of the player, they would look slightly left so they are facing towards the wall, and hold W, A and Sprint. Wall running can also be done whilst crouching. This is done by doing the same key combination as mentoined before, apart from instead of Sprint the player would press Crouch. This allows players to move quickly yet silently.
The increase is quite minor but definitely a skill that must be mastered, especially for SMG's who may need to rush past incoming grenades. An example of a good wall to practice wallrunning on is on Backlot Defence spawn, just infront of the player and towards the right is a low wall that is perfect for wallrunning on in order to gain a speed boost into A bombsite.