My passenger side mirror was damaged by a security gate. The black housing broke free, but the silver back appears to be OK. The glass broke, but the backing plate looks OK. I decided to try to repair the unit. I epoxied the housing back in place and popped the back on. My question - how does the mirror backing plate get installed? There is a metal wire clip on the outboard side (I think) and a round split shaft in the center. Is that it, or am I missing something? Thanks!