Flat Shank Brushes are used to apply lubricant to chains and other moving surfaces.  The wisking action of the bristles evenly distributes the fluid as it reaches the contact surface.  Brushes can also help prevent dirt build up.  Bristles are available in nylon or stainless steel.  Flat brushes have an aluminum holder with a female thread to attach to a mounting shank or directly to a supply line.  A replacement brush is also available that  slides into the holder.