This single block is typically used on the boom of a Catalina 42 or Catalina 445 for the mainsheet or Catalina 387 spinnaker halyard.

To prevent the line from twisting or binding when used in a cascade or mainsheet system this block is supplied with a feature to lock the rotation of the shackle that is on top of the body of the block. With the use of an Allen wrench, tighten the set screw to lock the shackle in position. When used as a swiveling block, ensure the set screw is not tightened and the swiveling shackle can self-align to find the fairest lead.

Approximate Dimensions:
• Shackle pin diameter: 5/16"
• Sheave diameter: 3-1/4"
• Maximum line size: 5/8"
• Bearings: Torlon
• Safe working load: 3500 pounds C-455