There was the thumbscrew, an instrument which smashed the thumb to pulp by the turning of a screw.
The pressure can be adjusted by the thumbscrew on the balance.
The valve should be of the "screw-down" pattern, either with a thumbscrew, wheel and spindle, or a key.
"Yes, I expect the thumbscrew hurt," said Reggie, meditatively.
Proper adjustment of the thumbscrew and bar makes the box ready for use.
When the measure is set, make the thumbscrew as tight as possible with the fingers.
The front flange of this device or gage may be slotted and fastened to the table by a thumbscrew.
When the back gage is set, tighten the thumbscrew with the hand.
This must have been a thumbscrew for the Secretary when he presently read the pamphlet that escaped his officers.
But that thumbscrew has got me guessing, as our American cousins say.