The ROD type device is a temporary fluid dynamic restraint or shock transmitter unit (STU). The ROD device allows slow displacements with a low reaction force, while in contact with impulsive forces it behaves as a fixed restraint. Its behaviour is symmetrical with respect to the intermediate position, both in terms of reaction and displacement. This type of operation is due to the presence of a piston inside the steel liner that divides two chambers containing hydraulic fluid and connected via a calibrated valve. For slow movements, the viscous properties of the fluid allow displacement; for impulsive loads, the pipe between the two chambers creates an obstacle to the flow by blocking the piston. Two spherical hinges connect it to the structure, allowing rotation around any axis. The device acts like a connecting rod, only able to transmit forces along its axis.