A thumbscrew was a tool used long ago to hurt people on purpose — usually to make a prisoner confess. The thumb was put in it and the screw was turned, slowly crushing the thumb. It belongs with the other machines of old torture chambers, and you mostly meet it in history books, museums, and films. Because of that history, the word lives on in a picture: 'to put the thumbscrews on someone' means to put heavy pressure on them, pushing harder and harder until they give you what you want. 'The bank is putting the thumbscrews on small businesses' — nobody is being hurt; they are being squeezed. In this use it is almost always plural, thumbscrews. There is a second, completely harmless meaning that is common in everyday life today: a thumbscrew is also a screw with a wide flat head or two little wings, made so you can turn it with your thumb and finger and do not need a screwdriver. You will find them on computer cases, camera stands and bicycle parts. The same name, two very different things — the shared idea is simply the thumb doing the turning.

拇指夾（古代的拷問刑具）；也指用手就能轉的「手轉螺絲、蝶形螺絲」。片語 put the thumbscrews on someone＝施壓、逼迫。