Easily identify which ewes have been bred with this all-weather marking crayon Designed for use with our Nylon Ram Marking Harness, Leather Marking Harness, or Pedigree Cotton Marking Harness Crayons easily slide into place and are secured with a cotter pin for a reliable fit Simply slide the included cotter pin through holes on side of harness holder and crayon, then bend the end of the pin with pliers to lock in place