How do these work?

The plastic tubes go on the ends of pegs facing out so you don't hurt yourself when reaching in. I'm not sure what you mean by "bits"., but the long skinny ones go across a single peg so it doesn't always fall out when you remove something. Hope I covered what you asked. If not, ask again but be more specific.

Are the tubes used to cover metal hook protruding from board? The black tips are probably designed to cover the exposed end of the hook to avoid injury to exposed skin.