"U" shaped cutouts on a PC Case

[El Moriana]

I'm asssuming most people have opened a PC case at some point.

What are the "U" shaped cutouts lining the edge-flanges of the case there for?
There are also curious little raised circles on the inner part of the "U" shapes. I've always noticed them but I've never known what they actually do.

Does anyone know?

[rcgldr]

If you mean the rubber or plastic material used to cover the internal edges of the case, it's because those metal edges are sharp, and those edge covers prevent people from getting cut or scratched when working on stuff inside the case.