Sanding discs smooth surfaces made of metal, wood, composites, and other materials. They remove paint, clean and level welds, remove rust, and prepare surfaces for finishing. Arbor-hole mount discs have a hole in the center of the disk to attach to the arbor. Quick-change discs mount to a quick-change backing pad to reduce the time it takes to switch out discs. Hook-and-loop discs mount to a hook-and-loop backing pad. They're used when discs are frequently changed out before they're fully worn out. Adhesive-backed (PSA) sanding discs have an adhesive backing that holds the disc to a compatible backing plate. PSA discs can only be attached to a backing plate once, so they're best suited for applications that don't require a lot of grit changes. Shank-mount surface-conditioning discs attach to die grinders and rotary tools to prepare surfaces for welding or finishing. Floor sander discs remove old finish, smooth imperfections, and prepare floors for final finishing.