Wire Blocks also known as backstay adjustment blocks have special sheaves to take the load and abrasion of the stainless steel wire passing through the block.
The sheaves are generally V shaped to match the wire and machined from brass or aluminium rather than nylon.
The construction may be more robust and built to withstand greater loads than some rope blocks.
Backstay adjustment normally starts with splitting the backstay to create a 2:1 initial purchase. Backstay Wire Blocks are fitted to the end of the single (top) part of the backstay so that the bottom section of flexible wire can be fixed to one aft quarter, reeved through the backstay block and attached to the backstay adjustment system. The adjustment system is then attached to the other aft quarter.
Select a Wire Rope Block from tried and trusted brands - Selden and Barton.