Harken 57mm Carbo Air® Fiddle Ratchet Block with Becket and Cam-Lock locking system allows the shackle to lock at 90 degrees.
Carbo Ratchet fiddle blocks allow sailors to hand-hold loaded lines and offer a balance between holding power and controlled easing. Lightweight Carbo Ratchets are available in 40mm, 57mm, and 75mm sizes. All the Carbo Ratchets feature a recessed On-Off switch that is easily operated from either side. The 40mm cam-arm versions work in ratchet mode only. Commonly 57mm fiddle blocks are for dinghies and small keelboats.
The 40mm, 57mm, and 75mm Carbo Ratchamatic® iare adjustable for many applications and weather conditions. The load-sensing ratchet block rolls freely in both directions under low loads and then engages the ratchet automatically as loads increase. With a 180-degree wrap, you get a 10:1 holding power.