The Glass is held by COMPRESSION. The use of the Security Pin is OPTIONAL Stainless Steel AISI 316 Marine Grade Suitable for Indoor and Outdoor areas The item includes: (4) glass clamps, (8) gaskets for 3/8" glass, (8) gaskets for 1/2" glass, (8) gaskets for 9/16" glass,, (4) safety pins Compatible with 3/8" or 1/2" or 9/16" tempered or laminated glass (Pack of 4) Square shape 2.17" x 2.17" (55 mm x 55 mm) The Marine-Grade 316 Stainless Steel Square Glass Clamp [2.17"] for Flat Surface offers a modern design, straightforward installation, and a secure fit. It mounts easily to metal surfaces with bolts or to wood with lag screws. A built-in safety pin provides added protection, while the glass is held in place by compression. The clamp includes rubber gaskets for 3/8", 1/2", and 9/16" glass panels. Mounting hardware (screws, bolts, anchor bolts, etc.) is not included and should be selected based on the installation surface.