I found this stray piece in a box of non-Playmobil bits and pieces while tidying my son's bedroom.
My first thought is it looks like part of a ladder. There are 2 bumps on the outside edge which look like they would help it click into another piece.
I can't for the life of me remember which set it is from. He has quite a lot of Police sets and some Dino Expedition stuff so maybe it's from one of those.
(Btw, it looks black on the pic but it's dark grey.)