#rein  one of a pair of long straps (usually connected to the bit or the headpiece) used to control a horse
  supertype:  strap  an elongated leather strip (or or strip of similar material) for binding things together or holding something in position
  part of:  bridle
  subtype:  bearing_rein__bearingrein__checkrein  a rein designed to keep the horse's head in the desired position
  subtype:  leading_rein__leadingrein  rein to direct the horse's head left or right

No statement uses or specializes rein; click here to add one.