English: This weighing scale measures the weight of an object using an internal spring and its known spring constant. It can be affixed to a stationary object by the hook on top, while an unknown weight hangs by the hook on the bottom, deflecting the spring and moving the weight indicator along the graduated scale printed on the spring housing. A knob on the side of the spring housing allows the user to calibrate the weighing scale to zero. This sort of scale can also be used to measure any force in any direction transmitted through the scale. Source: http://www.hq.nasa.gov/alsj/tools/judy58.jpg