The Carbo Ratchamatic is a load sensing ratchet block that rolls freely inboth directions under low loads and automatically engages the ratchet as loads increase. Shifting between ratchet and light air modes is seamless. Unloaded main and jib sheets run out freely during mark roundings and asymmetrical spinnakers free instantly during jibes. Ratchet engagement may be adjusted to a higher or lower load according to strength and sailing style. The Ratchamatic cheek block mounts on either port or starboard. The holding power of the 57 mm is as high as 10:1. The 75 mm is up to 15:1. For the ultimate system mount a switchable ratchet in the cockpit and a boom-mounted Ratchamatic directly above for double holding power in heavy air and a free-running mainsheet when it's light. Use the 2634 with a 402 or 403 swivel arm for a versatile two-speed mainsheet system