If I remember,,, and that's a job,,, undo the lock in the rubber put the rubber in the hole and VERY carefully work the rubber around the glass,,, use a soap solution to lube things up,,,, there is a tool, but I never used one, just a regular screwdriver. If the rubber is all hard you might want to get a new one. It a tedious job, just take your time,,, price out the glass before you try it,, it may give you the patience necessary?