The roller on the back of a loom that changes the angle of the yarns coming off the warp beam to feed into the harnesses. Also used to control the angle at which the yarn enters the harnesses and the resulting tension on the warp yarns. As the roll is raised or lowered, the appearance of the cloth will change. The whip roll is also timed to move forward as the harnesses rise to decrease the tension on the warp yarns.