Proper Removal And Insertion Of Glock Frame Pins
REMOVAL: Working from the LEFT SIDE of the frame, begin by using either an Armorer's Tool or a 3/32" Machinist's Drift Punch to push out the topmost, #1, 'lock block pin' first.
Next, while continuing to work from the left side of the frame remove the middle, #2, 'trigger pin'. (You might have to wiggle the slide stop around in order to loosen this pin.)
Finally, still working from the left side of the frame remove the lower, #3, 'trigger housing unit pin' from the back of the pistol's grip.
INSERTION: Now, working from the opposite RIGHT SIDE of the frame insert the #1, 'lock block' pin back into the pistol BEFORE you attempt to install any of the other pins.
The next step is to make sure the slide stop is installed, and in its right place on the pistol. (Obvious, I know; but it should, still, be mentioned.)
Depending upon whether you believe the Armorer's Manual, or not, either Pin #2 goes in next, or (for some goofy reason) Pin #3 is presently recommended to go in before Pin #2. (Like a Glock's cheap plastic frame is a precision rifle stock!)
Personally, I started out 10 years ago using the previously recommended order of: '1, 2, 3' for both removal and insertion; and, at the present time, I have absolutely no good reason to change. On my Glock pistols the #2, 'trigger pin' goes back in second.
If you have trouble getting the #2, 'trigger pin' reinstalled into its frame hole, simply giggle the slide stop up and down, or backwards and forwards until it slips in.
Do NOT push too hard on any of the pins, or do something 'YouTube stupid' like banging, or even tapping, on a pin with a hammer. (A hammer or a knife NEVER needs to be used on Glock pins.)
NOTE #1: IT, ALSO, HELPS TO USE THE SHAFT OF YOUR ARMORER'S TOOL IN ORDER TO ALIGN THE PARTS BEFORE YOU BEGIN RUNNING EACH PIN INTO ITS RESPECTIVE HOLE.
SIMPLY SLIP THE TOOL'S SHAFT INTO THE PROPER FRAME HOLE, AND TWIRL IT AROUND UNTIL THE RESPECTIVE PARTS ALL LINE UP. (YOU WON'T SEE ANY PROTRUDING EDGES WHEN YOU LOOK INTO THE HOLE.)
NOTE #2: WHEN YOU GET CLOSE TO THE FRAME, PLACE THE TIPS OF YOUR FINGERS ON THE TIP OF THE ARMORER'S TOOL AND FINISH PUSHING THE PIN INTO THE HOLE IN THIS WAY. (YOU'LL BE LESS LIKELY TO SCRATCH THE FRAME IF YOU DO IT LIKE THIS.)
NOTE #3: 'RIGHT' AND, 'LEFT' ARE DETERMINED BY WHAT WE USED TO CALL, 'MACHINIST'S CABINET VIEW'.
HOLD THE GLOCK AS YOU NORMALLY WOULD IF YOU WERE POINTING THE MUZZLE AT A TARGET. NOW, LOOK DOWN ON THE TOP OF THE PISTOL. THIS VIEWPOINT CORRECTLY SHOWS THE PROPER RIGHT AND LEFT SIDES OF THE FRAME.
ADVISORY: I am NOT a Certified Glock Armorer! (I'm only that armorer which Gaston Glock has forced me to become.)