on hydraulic and pneumatic design, a hand pump is usually
operated by hand by the usage of a lever or handle.
When external force is applied manually, it actuates
an internal mechanism that increases pressure for moving
fluids including water, chemicals, or gas. The hand
lever is pushed in an up and down motion, which begins
the pump cycle. Often one motion is required to draw
the fluid and another motion is to release the fluid.
This technique is typical for the operation of displacement