If you don’t know what wall hopping is, it’s basically a glitch that allows you to jump on certain walls. This can be both done in R6 and R15 but is much easier to do in R6.
This can be easily done with all parts that are on top of each other. You can also make a ladder by placing parts on top of each other (With a gap) but with no gap, you can simply wall hop it. But how do you stop it? It’s very simple, actually.
Figure it might also be worth explaining why this is possible in the first place and how replacing collisions with a single non-collidable block can resolve this issue. This happens primarily because Humanoids use raycasts to stay on top of objects and the edges between parts constitutes a valid surface, pushing the character above. This method just defines a single collision space and the raycast won’t catch on because the next valid edge is at the top of the brick.