The most difficult tools riddles

The reason for the clockwise orientation of most screws and bolts is that supination of the arm, which is used by a right-handed person to turn a screw clockwise, is generally stronger than pronation; while screwing is generally done more often than unscrewing.

For bicycle pedals, the screw on the right must be reverse-threaded, or the pedal will unscrew during use, being subject to counterclockwise torque (which would work to undo a right-hand thread).

An opisometer, also called a curvimeter, meilograph, or map measurer, is an instrument for measuring the lengths of arbitrary curved lines. A simple opisometer consists of a toothed wheel of known circumference on a handle. The wheel is placed in contact with the curved line to be measured and run along its length. The instrument is most commonly used to measure the lengths of roads, rivers and other line features on maps.

Scissors will not cut properly if held in the wrong hand, and are manufactured in both lateral varieties. However, since right-handed version is common, most left-handed people learn to operate scissors with their right hand.