Rounded, undercut headCommonly used with washers and nuts, or driven into tapped holes18-8 Stainless steel spanner pan head machine screws are corrosion and rust resistantSuitable for fresh water moisture environmentsCommonly used for:Restroom StallsSchoolsCarsBoatsElevatorsLicense Plates Spanner pan head tamper proof security screws with a Spanner (Snake Eye) drive. Spanner security screws are used for securing materials from being tampered with. They are commonly used in food prep and processing areas, elevators, boats, and any public space. The spanner drive has an unusual drive style making it harder to tamper with. These screws are often used to deter vandalism in public areas where tampering is more likely to occur. Matching bit not included. Tamper Proof Security Screws with an Pan Head and a Spanner Security (Snake Eye) Drive 18-8 Stainless Steel Screws Spanner Pan Head Machine Screws are made from grade 18-8 Stainless Steel, which means that they are corrosion and rust resistant is applications exposed to moisture. This is an ideal quality for tamper proof fasteners, as they are often used in outdoor, public spaces and meant to last. Spanner "Snake Eyes" Drive Spanner security screws (also known as drilled spanners or snake eye screws) feature a highly unconventional drive style, engineered to resist loosening with standard tools. Spanner drive screws can only be installed or removed using a matching bit, which is NOT included. Pan Head Pan head screws feature a rounded head (less so than a button or round head) and a flat bottom designed to sit directly on the installation surface.