Everyone is confused about the clothespin.
Clothespin? • /r/112263Hulu
I took it as his parents abused him or some shyt he's into weird sexual masochism
I think that's pretty much it, to show that he's a sexual weirdo. In the book, Clayton is super OCD and he tells Sadie that she's disgusting for ever wanting to have sex and makes them sleep with a broom in between them. The clothespin thing is kind of a weird spin on it. They could've just kept the story the same as the book to make it less confusing.