A hydraulic hand pump is a manual device used to generate hydraulic pressure using a hand-operated lever/handle. It is commonly used as a compact hydraulic power source in hydraulic systems, especially for emergency operation, standby use, commissioning activities, and manual pressure generation where electric or pneumatic pumps are not available.
Hydraulic hand pumps are widely used in:

hydraulic power units (HPU)
wellhead control panels (WHCP)
offshore hydraulic systems
valve actuator operation and testing
hydraulic equipment commissioning
hydraulic pressure testing and maintenance tasks
It is especially useful as a backup pump when main power sources fail.