R614-5-1. Crawler Locomotive and Truck Cranes

Two-Blocking Damage Preventive Feature. On hydraulic cranes with power telescoping booms, an "Anti Two-Blocking" feature, warning device, or other arrangement, shall be provided to warn the crane operator to avoid colliding (two-blocking) the hook block with the boom point when hoisting the load, when extending the boom or when booming up or down.