Cannon chichester replacing white cap ends for oven inner glass on door?

Hi I have a cannon chichester gas cooker ,the cap ends have broken which form a ledge that supports the inner glass that slides in on the main oven door.I have bought 2 replacement white caps from cannon managed to replace outer one .Could you help explain how I can replace the inner one which the rod goes through that holds the door in place would appreciate your help .

Mary
September 2013