Take some fresh masking tape (if you have a pretty old roll, forget it, go to the store and get some). Cover the checkering completely using masking tape. First, work your fingers good over the checkering, working the tape down well. Nest, using a plastic butter knife, press deeply but carefully into the outer borders. Grab a sharp razor knife or exacto and --carefully-- cut into the outer border groove, trying to cut the tape but not the wood. Then, remove the tape outside the cut lines.

This leaves a thin armor of masking tape in the checkered areas. You can then work up to the checkering with sand paper and not worry as much about hitting the diamonds. It won't stop a piece of 60 grit on a palm sander, but it can really save you if you're working carefully with hand sanders or the like and slip a little.

This tip also comes in very handy when camouflaging synthetic stocks. It leaves the checkering black, giving the gun a nice custom look. You don't get points if you don't remove the action, bottom metal, recoil pad and sling studs though!