A screw gauge is a precision physics laboratory equipment/instrument used to measure small dimensions ranging from millimeters up to 5 cm.

Essentially, it has the least count of 0.01 mm, moreover, allowing measurements in very small increments. Additionally, the device works using a screw mechanism, where rotation of the thimble moves a spindle forward or backward over the object being measured.

It is widely used to measure:

The diameter of thin wires
Thickness of small sheets
Dimensions of screws and bolts