Thumbscrews are another device that has been in use for few thousand years but became especially popular during in medieval Europe. They can be used in a similar fashion to hand cuffs to restrict the subject or they can be used as torture devices if the pressure on the fingers is increased. Some thumb screws have spikes or blades on the inside to inflict even more pain.
Thumbscrews can be build fairly easy yourself. Take two metal or wood strips of about 6” length. The width determines how much pressure will be put on the fingers. 1” (2.5cm) is standard but thinner is doable. Drill holes toward the ends of the strips and then use regular bolts and wing nuts to create the pressure.