A Chain pulley block is a tool used to lift and lower heavy loads utilising a chain. Two wheels are functioning in it which the chain is wound around. When the chain is dragged, it winds around the wheels and starts to lift the item that is connected to the rope or chain via a hook.What are Chain Blocks The Chain Block is a mechanism used to raise or lower heavy loads with relative ease. The internal gears of the Chain Block wind the chains around, lifting the object that is attached to the end or hook. This means that very little force is required to lift large, heavy loads of up to 30,000 kg.