The Star Exercise Tool provides a means of locking into the opening prong of a tubing retrievable safety valve if the operator has a valve with an opening prong/piston that will not operate.
This tool is designed with spring-loaded keys to allow them to flex in when travelling through the tubing string. As the exercise tool enters the opening prong, the 90° bearing surface on the keys contacts the shoulder of the profile in the opening prong and stops the tool string. The operator can jar up or down to try to move the piston/opening prong of the tubing-retrievable safety valve to make the valve operate.
To retrieve the exercise tool, jar up to shear the spring-loaded shear pins.