In some of the top speedruns you'll see speedrunners wallrunning over and over again on a wall to gain massive height. This looks tricky but is actually really simple.

All you have to do is look straight up as you're going towards the wall, and at the correct angle to wall run. Once you reach the wall, jump as fast as you can over and over again.

This also works at a corner of two walls, but doing that is slightly less reliable.