A sailboat block is a nautical pulley system used to redirect lines and increase mechanical advantage, making it easier to manage high-load ropes like halyards and sheets. It consists of a sheave (wheel) enclosed by cheeks (sides) and held together by metal straps and a pin. They are crucial for controlling sail trim and reducing crew effort.

Common Uses

Mainsheet Systems: Control the main sail's angle.

Halyard Blocks: Route lines down the mast to the cockpit.

Lead Blocks: Manage lines along the deck or mast.

Boom Vang/Backstay: Adjust sail shape.

Blocks are often chosen based on the load they must handle (plain vs. ball bearings) and how they are mounted (swivel, fixed, or stand-up).