The Harken 57 mm Over-the-Top Double Block (Part 3003) is a robust, high-load sailing block designed to guide lines aft over cabin tops, coamings, or splashguards for clean routing and easier trimming. Its dual sheaves help create purchase systems or lead lines smoothly from above toward deck or cockpit. With a 57 mm (2 1/4″) sheave, it accepts ropes up to about 10 mm (3/8″) and offers a maximum working load of ~1136 kg (2500 lb), with a breaking load of ~2272 kg (5000 lb) — strong enough for halyards, sheets, or control lines on mid-size cruising or racing yachts. Over-the-top blocks are typically mounted via multiple fasteners to structural deck or mastbase hardware and are ideal where you need a high-load, low-profile line redirection over cabin or deck structures.
