Thanks David for the link! Torvald: Good tip! No need to completely remove the back. Richard: Thanks for the heads up on screw length. Ian: I don't know about the 420 but on the 510 the 3rd screw was difficult to find. It's on top, sort of under the strap link. I'm VERY unhappy with the design of this door. I don't abuse my camera and yet the little plastic tab broke off. And it's not easy to find a new door. Terrible design by Olympus!