Harken 1 Ton Twing Block1 Ton Twing Block The Twing block features a spring loaded side opening mechanism for true one handed rigging, even while wearing sailing gloves. Black anodized aluminum sideplates are edged with robust bumpers to protect the block, topsides, and deck. The sheave is aluminum rolling on a bearing system shared with Harken's existing 2. 3T high load snatch block. Features: Side opening side plate Easy to rig and remove from sheet Spring loaded button