The Otapin, how to make a loaded Glock pistol completely safe and unfirable yet can be fired in less than a second by pulling the Otapin out.  I have been using my own Otapin since 1995, with no problems of any kind.  The one-inch key-ring makes removal easy.  How it works is that the slide is held back and out of battery by 6mm.  The pistol's own disconnector functions makes the striker and trigger inert.  If you need to shoot, just pull the Otapin out and fire away.  17 years of functionality behind it.  The Otapin is held firmly in place by the recoil spring power.  If some criminal pulls your Glock out of your holster, they will have an inert firearm in thier hands, giving you the time to get the pistol back or the criminal knocked out or shot by your back-up gun.  The Otapin is installed by pulling the slide back about a centimeter, and then the Otapin is installed straight down just to the left of the barrel hood.  The slide is then released, and the Otapin is held in by the recoil spring power.  It takes a moderate force to pull the Otapin out, but it all WORKS.  Keep your Glock SAFE with the Otapin.