There is a controllable valve on the piston inside the lockable gas spring The piston rod of the lockable gas spring is hollow, with a thin rod in the middle. The push and pull action of the thin rod can be controlled by the wrench device on the head of the piston rod, and then the thin rod drives the controllable valve on the piston to open and close. When the controllable valve is opened, if no axial external force is applied, the lockable gas spring will extend and the piston rod will be pushed out. If there is an external force greater than the force generated by its internal pressure, the lockable gas spring will be compressed.