Single Switchable Ratchet With Fiddle. The Pro-Ratchet 50 features a hardwearing nylon sheave with eight V grips to give an extreme hold on any rope. In the middle of the block is a switch that can be used even under load to turn the ratchet on or off. This fiddle version is ideal for use in a 3:1 mainsheet system. The large hole through the fiddle can also be used as a becket. Located at the head of the block is another switch which can be used to lock the swivel in 90-degree orientations.