The conventional method to remove wave-dissipating blocks placed in ports and shores is that hanging up the blocks by cranes after making the wire ropes go around the blocks by workers or divers. This method is not always safe because it is unstable work, and the working efficiency is not sufficient because it is troublesome work.
　Some transfer machines which use no human power have been developed and introduced in actual work.
　However, as their power units to drive chains or fingers are built inside the machines, their weight is equal to or heavier than that of a block to be removed. Consequently, the working efficiency is increased but the cost is not reduced because floating cranes of larger capacity are necessary.
　To reduce the cost, I invented a lightweight transfer machine for blocks using net chains, which has no power unit because it is driven by the winding power of crane winch. This machine spreads net chains over the block, pulls net chains by wire rope of the crane to catch the block tight, and hangs up the block. We made a small model of this machine and carried out model block transfer experiment. Moreover, we carlied out removing work of 2-ton wave-dissipating blocks by life size trial model.
　The effectiveness of this machine has been verified through these experiments, and the working efficiency and the cost have also been calculated on trial.