Fish scale the surface, interacting only with the riblet tips, not causing any high-veloctiy flow in the valleys. Since this high velocity flow now only interacts with the riblet-tip, which is a very small surface area, the momentum transfer which causes drag is now much lower than before, thereby effectively reducing drag. Also, this reduces the cross-stream velocity fluctuations, which aids in momentum transfer too. The rough, sandpaper-like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was
Leather wallpaper Leather wallpaper Leather wallpaper is a type of wallpaper used in various styles for wall covering. It is often referred to as wrought leather. It is often gilded, painted and decorated. With the advent of wallpaper use from about 1650-1750, leather was used to cover and decorate sections of walls in the habitations of wealthy persons. Leather is pliable and could be decorated in various ways. Embossed wall coverings made to imitate antique embossed leather include Tynecastle, or Modeled Canvas. It was developed and patented in 1874 by designer W. Scott Morton (1840-1903). It was made by hand pressing canvas