The nylon rivets used to secure  Core One panels have two parts: a pronged collar, and a pin which goes through the collar. There are several tools on Printables which work by inserting a lever under the head of the pin and pulling it out like a nail remover, but these can be difficult to get under the head of the pin, and can scratch  acrylic parts or exert excessive force on the head. They can be used to push the pin out from the inside, but the lever is often blocked by printer parts like rods in the chamber.

The most effective way to remove the pin, and then the collar, is to press up on the shaft of the pin with your finger, which can bend around chamber parts. All of the rivet pins in the Core One are easy to reach with a finger, but pressing on them can be painful unless you have tough fingers!

This thimble protects the fingers and has a dimple at the top which locates into the tip of the rivet. To use it, press on the tip of the rivet pin shaft until it is flush with the flange of the collar. The head of the pin can then easily be pulled out with either fingers or one of the existing tools if you like.

I have included a SCAD file so the internal diameter of the thimble can be customised to the user's finger size.

Printing tips: Works with any filament type. I suggest setting seams to random so the the small dimple at the top of the thimble doesn't have a seam line to impair locating over the rivet.