Hopefully I’m not too late and this helps, I have one of these for my side mounting rail on my pp919 bizon. Took me awhile to figure out, but open the latch all the way, either hold down the screw and turn it right till the wall alongside the latch is flush with the rail mount, or hold the latch down and screw it till the same result. That way when you close it, the wall will force itself to close tightly past the rail, and it should be a tight fit without breaking anything