One-Way Tamper-Resistant Security Screws
One-Way screws are available in a round head design in both machine and sheet metal type in sizes ranging from #6 to #14. They are slotted screws, and can be installed with a standard slotted screwdriver. However, removing them without the proper one-way removal tool is difficult. Half of each side of the slot is smoothed down during manufacture. When you try to extract the screw, the slotted screwdriver tip will not grip and rides out of the slot. The screws are case hardened, zinc plated and stainless steel.