The SAF-T-BLOK helps reduce the possibility of accidental discharge when handling, carrying unconventionally, in a fanny pack, tucked in a belt or in your pocket. It snaps into place behind the trigger, providing a positive trigger block. The SAF-T-BLOK is adjustable to compensate for tolerance differences between different models of GLOCK. Adjust the nylon set screw with a 1/16" Allen wrench so that the SAF-T-BLOK ejects instantly by pushing the ejector with the index finger. Insert and eject the SAF-T-BLOK several times to become familiar with feel and operation. Always unload firearm prior to installation.