In this picture, the release button has been pressed, causing the rear locking flap (the level 3 lock) to release via spring tension. If you don't see it, look at the weapon's hammer, which the cap previously covered. The flap is directly above the hammer.
The pistol and holster have been flipped around, in order to permit access to the primary (level 2) release. You will notice that my Sig is equipped with Crimson Trace grips, and the Serpa holster doesn't interfere with the laser diode (located just above the upper grip screw) at all.
In this picture, I'm pressing the primary release. This is a lever which lifts the locking tab that clamps onto the trigger guard. It's spring loaded, so unless you simultaneously press the release and pull on the weapon, it won't come out of the holster.
While keeping the release button pressed, the pistol is pulled out of the holster. It doesn't have to travel very far (just a fraction of an inch) before you no longer have to keep the release pressed.
main Serpa article, and this article will strictly cover the holster itself. This picture shows everything that comes with the Serpa Level 3 holster. As you can see, the belt clip attachment (the large dark item towards the bottom of the image) is a separate module from the holster itself. This is so that, instead of producing a large number of holsters with varying methods of attachment, Blackhawk can produce a few standard attachment modules and a large variety of weapon-specific holsters. Included with the holster are two sets of three screws. The shorter set is used if you're attaching the holster directly to the belt attachment, and the longer ones are used if you want to use an offset spacer to increase the distance between the weapon and your hip. With or without the offset piece, the holster feels quite solid.
The three screw holes on Serpa holster are how you configure the holster's cant. In the picture above, you'll notice that the belt attachment has three slots, which are used to attach the holster to the belt. The reason they are slots instead of holes, is so that you can configure the holster to be vertically oriented, or canted forward or rearward. Note also that you can see some writing on the lower part of the inside of the holster. In addition to listing the weapons that this holster was designed to fit, this area also lists the holster's individual serial number. My holster indicates that it'll accommodate the Sig 220, 226, 228, and 229 models.
This is the vertical position for the holster.
This is the forward-canted position.
This is the rearward-canted position. Notice that, in each of the positions above, the screws are positioned at the ends the slots they're in, with no room for travel. I found the positioning of the slots and holes to be fascinating - you'd think that a design where the screws are all in slots instead of holes would result in a mere tension fit and considerable wobbling, but movement isn't possible with the angles used when all three screws are in position.
Canted rearward, with the screws installed. I found this to be the most comfortable way to draw, although it technically does make it a bit easier for someone behind you to grab your weapon.
This switch, meant to be pressed with your thumb before drawing the weapon, releases a spring-loaded "cap" which normally covers the hammer and rear of the slide.
Pressing down on the switch moves a small tab on the side. It's worth knowing that the tab is not angled - in order to re-lock the retention flap, you must press the button; you can't just close the lock on the gun without pressing the button. More on this later.
When the switch is pressed, the spring-loaded lock flips up very quickly.
The level 3 retention cap is actually hinged at two points. The swell at the center rear of the device accomodates the pistol's hammer.
This is a closeup after the release has been tripped, causing the cap to flip into the upward, unlocked position. You can also see that the lower section is contoured at multiple points in order to hold the weapon securely. Take particular note of the release tab and the hole on the cap into which it fits when in the locked position. The release tab itself is rectangular. If it were tapered, you could press the cap down until it clicks in place. Although this may seem desirable at first glance, it actually wouldn't be. For one thing, a tapered cap would wear down or break far more readily than a rectangular one. But more importantly, if you prefer to keep your weapon in level two mode, having it arbitrarily "upgrade" itself to level 3 when you accidentally close the cap could potentially be life-threatening.
Another picture from the side, in the locked position. If you zoom in, you can make out the rectangular tab mentioned above.
Between the two points of the retention cap's hinges, you'll notice a fairly strong spring which powers the spring-loaded level 3 lock.
Slightly left of center, you'll notice the primary release button, which is identical in appearance on all of the Serpa retention holsters I've seen. It's a lever switch, shaped like a capital L. The bottom of the L is where your finger presses while drawing your weapon. It pivots on a pin which you can see approximately midway up the L's vertical leg, and retracts a tab which sticks straight down into the weapon's trigger guard to a small degree. Unlike the secondary retention system, the primary system is designed not to require you to press the button in order for it up lock in place. The weight of a pistol dropping into the holster is enough to move the retention tab out of the way until the trigger guard has passed the tab, at which point the mechanism locks into place with a reassuring click. -- SeanNewton - 11 Oct 2008