Called fillets, filets, or wood slips, these all refer to the decorative wood strips most commonly used inside a mat opening. They can also be used on the inside lip of a frame. Fillets can be wood toned such as walnut or cherry, or gilt in silver or gold. Fillets come in infinite variety from simple round to heavily embossed. Most fillets may be toned to exactly match your frame and add a more classic formal look to your art.