Purfling is a narrow binding inlaid into the edges of the top and often bottom plates of stringed instruments. Purfling serves to reinforce the plates and prevent cracking along their edges.

Purfling was originally made of laminated strips of wood, often contrasting in color to add visual appeal. Later decorative abalone

Abalone

Abalone , from aulón, are small to very large-sized edible sea snails, marine gastropod molluscs in the family Haliotidae and the genus Haliotis...

 inlay was introduced to provide desired contrast. Today plastic purfling is commonplace in mass produced instruments, with the least expensive merely simulating purfling with paint.

Usually purfling is a sandwich of two black strips with one white strip in the middle, measuring about .033"W x .080"D (1.25 mm x 2.00 mm), but other variations are sometimes used.

The earliest known example of purfling is on a violin

Violin

The violin is a string instrument, usually with four strings tuned in perfect fifths. It is the smallest, highest-pitched member of the violin family of string instruments, which includes the viola and cello....

 made by Andrea Amati in 1564, now on display in the Ashmolean Museum

Ashmolean Museum

The Ashmolean Museum on Beaumont Street, Oxford, England, is the world's first university museum...

 at Oxford University.