Thumbcuffs are a metal restraining device that lock thumbs in proximity to each other.
Thumbcuffs were originally intended for use by detectives, narcotics officers and off-duty policemen, their size allowing them to be carried in the pocket.
Most are rigid devices, while some used in Asian countries are chain-linked, like miniature handcuffs.
Thumbcuffs are rarely used due to an increased possibility of injury, most commonly by tight cuffs blocking blood circulation.
[4] Thumbcuffs may also be used as improvised toecuffs by locking the big toes in proximity to each other.