A soroban (算盤) is a wooden board with triangular wedges or steps cut into it. It is traditionally associated with Japanese bondage. The soroban is used during the practice of Ishidaki (石抱き), where a person is forced to sit kneeling--called seiza (正座) in Japanese--on the board, then stones or other weights are placed on top of the thighs to increase the pain and pressure on the shins. Sometimes this device is simply called a kneeling board.
Origins of the Term
The word soroban means abacus in Japan. The ridges on the board are said to resemble the rows of beads on a traditional abacus.
Safety
The soroban is a torture device, meant to do harm. When used in the wrong way it can cause permanent nerve damage to the lower legs, especially around the ankles. Prolonged and/or repeated exposure to it can increase this risk.
