When the drawer is out hold the rail and push the drawer back in a couple of inches. The shim has to have a bit if a bend in the end. Slid the shim in past the catch and then pull the drawer out again and the shim will compress the spring catch and allow the stop on the drawer past. The stop on the drawer stop must be on top of the shim to pass the spring that is riveted on.Pull the drawer out as far as it will come. Slide a piece of shim stock or possibly a hacksaw blade with the teeth ground off into the track. Then push the track in. You may be able to do one side and then the other.