I have a TLR-1 and it mounts to both my TM G17 & P226 without sliding off.
Also, you
cannot slide the TLR-1 into position with the key...it is not meant to slide on!
To install it properly, you must back off the spring loaded screw and press it in which opens up the clamp...then you mount it from the
underside of rail!
You need to have the key installed in this position: