Which type of jack is utilized to hold a load permanently?

The screw jack is the type of jack utilized to hold a load permanently. This mechanism seamlessly uses a screw thread to lift and sustain heavy loads. When the screw is turned, it moves vertically, allowing for precise height adjustments and a secure hold. The design of the screw jack enables it to maintain its position without requiring additional power source once the load is lifted and locked in place, which makes it ideal for permanent applications.

In contrast, hydraulic jacks, while providing significant lifting power, generally require a hydraulic fluid source to maintain pressure and thus are used primarily for temporary lifting. Pneumatic jacks rely on compressed air, making them suitable for fast, short-term lifting tasks instead of sustained holding. Ratchet jacks can also lift loads but typically involve more mechanical movement and are less stable for permanent holding compared to the reliable screw mechanism.