Tony Hawk's Underground: Wall Bounce

You can get stuck in the air by using this glitch to bounce off walls.

How to do it
You can do this glitch on any level with high walls. You must have Moon Bounce to do it. It is easiest on the school campus level. I will tell how to do it on this level. Go to the area that you would start the gap that breaks through the window. Use the Moon Bounce to go up the wall to the left of the window. At the top, jump to the wall that the window is on. If you did this right, you should bounce back on the wall you started from and you will keep boucing back and forth and get stuck.

Why this works
Physics.

Credit
User Jorbs3210 discovered this glitch by accident.