Inlay covers a range of techniques in sculpture and the decorative arts for inserting pieces of contrasting, often colored materials into depressions in a base object to form ornament or pictures that normally are flush with the matrix. A great range of materials have been used both for the base or matrix and for the inlays inserted into it. Inlay is commonly used in the production of decorative furniture, where pieces of colored wood, precious metals or even diamonds are inserted into the surface of the carcass using various matrices including clear coats and varnishes. Lutherie inlays are frequently used as decoration and marking on musical instruments, particularly the smaller strings.

Inlay on guitars or similar fretted instruments are decorative materials set into the wooden surface of the instrument using standard inlay techniques. Although inlay can be done on any part of a guitar, it is most commonly found on the fretboard, headstock—typically the manufacturer's logo—and around the sound hole of acoustic guitars. Only the positional markers on the fretboard or side of the neck and the rosette around the sound hole serve any function other than decoration. Nacre, plastic and wood are the materials most often used as inlay.