My American friend gave my daughter a self-assembly toy and I want to ask her how to assemble it. I found the words rut, groove, ridge, channel and hollow. I want to describe the cuts or dents in some parts that are used to attach something to it. Is "dent" okay? I feel like this word is used for damages. I also saw pictures of 'grooves' on a vinyl record so I'm not sure if it is the proper word. Can you please also tell me in what situations I can use the other words? Thank you.
Please see the picture below. What do you call the hollow one and the protruding one that go together?