ring file

what is the ring end gap for not sure why it is filled or what is measured have i missed something here?

The end gap is there to make sure the ring ends don't "butt" together when they expand as the heat in the cylinder increases, which would damage the cylinder wall and it can even tear out the piston crown. It is measured by placing a ring (not installed on a piston) in the cylinder and using a feeler gauge to check the gap.