TRUGLO ONLY recommends sight installations be performed by a professional gunsmith with appropriate screw-type sight installations tools.
The square dovetails of the Walther rear sight are a unique design. What we recommend is to check the fit by hand first. If the rear sights starts nicely, then go right to the sight pusher.
If it the rear sight just barely starts, we suggest to carefully, cautiously file the rear sight dovetail to fit. Only file the front face and rear face of the square dovetail rails. DO not file on the top or bottom of the rails. Using a small flat file, start by just knocking off the black from the front and back of the rails. Then try installing the rear sight with the pusher tool. If it still feels tight, push the rear sight off, and file/dress the front and back of the rails again.
You will want the fit, to be a nice press fit, so it does not move by hand, but not so, tight as the slide shaves the dovetail. Most times, if it’s tight, just knocking off the black finish will make the rear sight fit much better. Be sure that the sight goes on straight & level. If the sight starts to twist, or angle, push the sight back a slight amount, check that the sight pusher is adjusted correctly, and start pushing again.
Make sure you are using a good sight pusher (TRUGLO uses the MGW Sight Pro). If you are trying installation with a hammer and drift it’s easy to ruin a set of sights and installation with impact tools will void the TRUGLO warranty. (attachment)
Use a good Loctite® (no red Loctite®) for the rear set screw and DO NOT overtighten as the slide is very thin under the rear sight. Maximum torque is 8 inch-lbs. Over tightening the set screw can damage the slide. You can use green Loctite® (620) on the rails, also, if you are concerned about the sight moving.
Engineering recommends your gunsmith to use the MGW Sight Pro tool and for the front sight screw, Blue or Purple Loctite® for fasteners.