This means nothing without context and the context is Making a "Wall Climbing" System - #11 by JimmyChance. But you already posted on that thread.
Whatever. He’s giving two options.
- Shoot a ray from the center of the character forward. If it hits something, that’s the wall that you wanna climb on.
- Keep track (somehow) of the walls to the left and right of your current wall. If you get close enough to the wall on the left or right, switch to those walls.