Critical Glock Armorer’s Tool – The Inspection Slide Plate Cover

Most people take for granted the simple, yet effective firing mechanism of the Glock pistols. And to his credit, Gaston did design and build an incredibly robust system that is one of the few portions of the Generation 5 handguns that did not see significant changes. The cruciform, trigger, and disconnector, combined with the slide cuts is a safe and reliable system.

What Glock did not account for was the now plethora of aftermarket options that attempt to improve upon the stock system. This is typically done through the heavy polishing of the various engagement surfaces (which unlike say an AR-15 trigger, there are more than one engagement surface) and to the detriment of some users, changes in the engagement geometries.

The latter can be quite dangerous if the manufacturer did not account for manufacturing variation and tolerance stack. In my case, I can speak to having a Glock go full-auto on me during a 3-gun match. The primary safety issue is the engagement between the firing pin and the sear ledge of the cruciform after reset. Often, especially when using different companies’ parts, the overlap of the two can be quite small.

Shooters not knowledgeable of the platform like this, as the smaller engagement comes across as a shorter trigger pull. That short pull comes at a potentially significant cost for safety. With highly polished surfaces and not enough engagement, its easily possible for the strike to release on reset, not on the trigger pull.

As such, anyone using aftermarket trigger parts for the Glock (or curious to see how their handgun works, should look to pick up an Inspection Slide Plate Cover, which is half an end plate designed so a shooter can see into their handgun and check engagement.

The parts in typically inexpensive, running about $3 from major online sources or coming as part of armorer’s kits like one from OC Tactical, which includes an exploded parts diagram mat, parts tray, and tool. A basic kit like the OC Tactical runs for $26.50. 


TFB’s FNG. Completely irreverent of all things marketing but a passionate lover of new ideas and old ones well executed. Enjoys musing on all things firearms, shooting 3-gun, and attempting to be both tacticool AND tactical.


  • Old Tofu

    no one’s made a clear one yet? c’mon internet get on it!

    • Grant

      It really would not do any good. The reduced height on these holds everything together while giving a better view of what is going on.

      They also allow you to reach in there and release the striker if things don’t fit like they are supposed to. This is kinda important because you can end up with a gun you can’t easily disassemble if the striker won’t release.

      • Old Tofu

        o sure , use logic against me 🙂

      • HSR47

        You can actually get the Glock tool in to release the striker with a standard backplate; It’s just harder, because you can’t see what you’re doing.

  • insider

    Not just for checking engagement, they also let you get the gun apart when adjusting an overtravel stop.

  • Rick O’Shay

    I seem to recall one of the shooting leagues banned aftermarket trigger mods on glocks? Am I not remembering this correctly? It was for the very safety issues mentioned here.

  • FightFireJay

    Also works on full size and compact (not Shield) M&P.

  • Seth Hill

    How can there be Glock perfection if there are aftermarket parts?

    • Lew Siffer

      Because every aftermarket part is junk that offers an expensive and dangerous solution to a problem that doesn’t exist. Yes, even the Glock sights work just fine out of the box.

      • Koolhed

        I once had a problem shooting lead projectiles with the factory Glock barrel and it was fixed by an “aftermarket, expensive and dangerous junk part.”

        • Lew Siffer

          My apologies. I forget that for some of us the Glock is a toy for recreation; I was only thinking of self defense and duty use.

          • Jai S.

            I have a Glock 20 that is used for outdoor self-defense. Hard cast lead are the best bullets for that use. The Glock struggles with accuracy there.

        • HSR47

          I frequently shoot poly-coated lead projectiles in my Glock barrels; I haven’t had any issues yet.

          • Koolhed

            Yes, I have some of those nice, wooden cases from ACME that hold my “red lipstick bullets.” They seem to be more than adequate.

    • Old Tofu

      how can people still have the same lame “perfection” question every time glock is mentioned. get over it already.

  • Tommy

    Great way to let crud into the works also

    • HSR47

      That plate is only intended to be used to check sear engagement between the striker and the cruciform. It is not intended to be used in place of a standard slide cover plate.

  • As a Glock Armorer I use this every time I perform an inspection. After breaking down the slide I put the slide back together with the orange inspection slide plate cover. After the frame has been inspected and put together I put the slide back on and examine the engagement of the firing pin lug and cruciform. There have been a few well-used pistols that clearly showed a reduced engagement from time and wear, but for the most part most Glocks continue to have good engagement. Prior to completing the final function and safety tests I remove the slide and replace the original slide plate cover. It literally takes a minute at most.