My daughter accidentally broke the bolt on a Velux window. It's a locking bold that slides in and out and can be used to hold the Velux window open. You can remove the bolt with a torx screwdriver, and the plastic can be forced out of the metal sliding rail. My model is not an exact copy, but based on the original part. It works well enough, but I recommend printing it with a filament that can handle high temperatures, such as PETG.