The paper gives an overview about reins and bits and their influence on the movements in horses. Based on anatomical specimens and resulting schematic drawings the various influences of bits and reins including recent results of forces, measured by some authors are described. The great variability in bits and reins makes it very difficult to judge their influence. The bit produces forces in ventral, dorsal and caudal direction. The ventral forces may damage the lower jaw. Especially the caudally directed forces hold up the anterior movement of the horse and areas as the temporomandibular joint, the neck and the caudal cervical joints may be areas of high load. There, rein forces are acting, which are considerably amplified by lever forces. The high forces induced by the levers of the curb or other bridles as the draw rein are pointed out. The bitless bridles may induce also pressure to sensitive areas as nose, neck or lower jaw. The most important nerves, which can be irritated by bits or bitless bridles are shown. The sensitive hand of the rider is able to avoid pain and damage to the horses head and enables controlled, but not restricted movements.