Spring Jar Calibration Tool allows quick and simple setting of the release force of the Spring Jar. The tool features a direct lead actuation plus accurate hydraulic load sensing.The Calibration Tool makes up finger tight on the Top Sub of the Spring Jar.The Tommy Bar is wound in and the jar latched.As the Tommy Bar is wound out the jar rod is pulled and the jar is released.The release force is read directly on the hydraulic gauge in pounds.