Cushion facings or "shims" are used to protect and firm-up the ends of the cushions. If you are replacing your cushions, get a set of these facings, which cover the ends of the cusions and rails, making them flush. A nicely-done installation job requires these. If you want to tighten your table, making it less forgiving, then get a few sets to “triple-shim” your table. These come in a set of 12, with 8 corner facings and 4 side pocket facings.