inlay

280px|thumb|Example of Boulle work inlay using [[tortoiseshell in mottled red, brass and pewter]] 280px|thumb|Boulle work showing the use of [[pewter (center) and the 'depth' given by tortoiseshell in the background. Brass inlay is on the right and left.]] 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.

Perhaps the most famous example of furniture inlay is that of André-Charles Boulle (1642–1732) which is known as Boulle work and evolved in part from inlay produced in Italy during the late 15th century at the studiolo for Federico da Montefeltro in his Ducal Palace at Urbino, in which ''trompe-l'œil'' shelving seems to carry books, papers, curios and mathematical instruments, in eye-deceiving perspective. The similar private study made for him at Gubbio is now in the Metropolitan Museum of Art.