A hand crank screw jack is a type of mechanical jack used for lifting, lowering, pushing, or pulling loads by manually rotating a handwheel or handle connected to a screw mechanism. It works by converting rotational motion into linear motion. Many hand crank screw jacks use acme screws that are self-locking, meaning they can hold the load in place without constant force or additional braking mechanisms. Ideal for applications where electricity or power generators are not available or are inconvenient. Can be used in various applications and configured as a single unit or in multiple systems linked together for synchronized operation.