Leverage and Spring Tension

I pressed my left foot against the flat end of a steel ruler on the desk. The opposite end lifted exactly two millimeters off the notebook paper. Releasing force allowed the metal strip to snap back with an audible vibration. Beside it, an upright black binder clip presented two movable wire levers. I secured my torso suction cup against its angled steel casing and pushed the forward arm down with both hands until it clicked flat against the wood. The spring resistance was firm and uniform throughout the pivot arc. Mechanical balance verified.