The Lock Mandrel is mainly used to provide downhole fixation for downhole fluid control equipment such as plugs, safety valves, packing tools, nozzles, etc. It is generally seated on the inner wall of the tubing, tubing couplings and preset working barrels; it can also be suspended for pressure Downhole instruments such as meters are used for dynamic monitoring of production wells;

Plugs are used to close pressure passages above and below a certain depth of the production string when repairing the Christmas tree, testing tubing, sealing formations, and setting hydraulic packers. Generally, the plug is connected to the lock cylinder with a rubber seal.