FYI the sights and that rear sight guard for that matter come off to the right side of the gun and go back on from the right side only.
I assume you're referring to the sight guard on his 4506? If so, the sight guard is only held in place by a 3/32" allen head base screw.
Once you loosen it the "winged" rear sight base/guard should come off with a slight tap as it sits flat on the top of the slide & over the access cover for the magazine & firing pin safety mechanisms.
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Adupuy, it's not very hard to do. You can make a spanner/forked wrench from a 1/4" drive flat tip bit or just use a tiny screwdriver to tighten the windage nut, then back off ~1/8 -> 1/4 turn.
You can flare the hollow end of the screw, where it passes thru the nut, with an appropriately sized punch & hammer, so it won't come off when adjusting the sight's windage.
It's basically the same procedure (see below) as for a S&W revolver rear sight blade replacement:
(FYI: The rear sight blade & it's windage screw are not the same as S&W revolver adjustable sights have even though at first glance they might appear so. (The diameter of the 3rd Gen's head is smaller than the revolver's, .185" -vs- .215"). However, the windage screw's nut is the same as the ones used on S&W revolver adjustable sights.)
S&W PN#s: 051070000 & 068480000, windage nut & screw, individually.
MidwayUSA PN#s: 672392 & 254171 respectively.
Smith & Wesson Rear Sight Windage Nut S&W 14 to 19 24 - MPN: 051070000
Smith & Wesson Rear Sight Windage Screw S&W 1006 39 - MPN: 068480000
(I'd suggest buying two sets of windage screw/nuts so you can have an extra if needed.)
As the diagram below shows there are a few springs & plungers to watch for (so you're not surprised) but if you're careful it's not difficult, if you're mechanically inclined.
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