A soutache is narrow flat decorative braid, a type of galloon, used in the trimming of drapery or clothing. In clothing soutache is used to conceal a seam. Often woven of metallic bullion thread, silk, or a blend of silk and wool, soutache began to be made of rayon and other synthetic fibers in the 20th century.
In military uniforms a particular width or color of soutache is used to indicate rank, particularly in a hat. In athletic uniforms a contrasting soutache is used to outline numbers or players' names.
The term is also used in bookbinding, where a narrow soutache is applied at the top and bottom of a book back to reinforce the spine and provide a barrier to keep dust out of the binding.