Designed For Use As A Guide On Large, Sliding Doors Up To 2-1/4" Thick By Side Mounting To Building. Embossed Frame With Two Wings Provides Greater Bracing And Holding Strength Versus Conventional Single-Support, Corner-Iron Frame. Delrin® Wheel Ensures Rust-Free Operation And Is Formed To Prevent Dirt From Clogging Or Accumulating. STAY ROLLER ZINC.