The glass clips on by the black plastic upstands on the back of the mirror glass. They are in a circle around the centre. When I took the glass out the second time , instead of levering from the side, I stuck the large suction foot from my satnav windscreen mounting onto the glass and it pulled off cleanly - any similar large sucker would do. You can see the clips if you move the glass to its full inward position and look from the outside edge.