Finger (unit)
[Exactly which part of the finger should be used is not defined; the width at the base of fingernail (#6 in the sketch) is typically less than that at the knuckle (#5).]
the fingerbreadth (literally the width of a finger) is an informal but widely used unit of measure.
[3][4] In the measurement of distilled spirits, a finger of whiskey refers to the amount of whiskey that would fill a glass to the level of one finger wrapped around the glass at the bottom.
"[8][9] Finger is also the name of a longer unit of length, used historically in cloth measurement, to mean one eighth of a yard or 41/2 inches.
These units have no legal status but remain in use for 'rough and ready' comparisons.
