Abstract: An adjustable mechanical device to engage the opening of a standard hydraulic floor jack to prevent said jack from lowering inadvertently in the event of hydraulic failure. Said device is installed by positioning as shown with L-clip under jack axle, and with adjustable strut extended so as to engage the upper shaft of jack. To remove the jack support, the lever is lifted wherein the pawl is disengaged, the strut lowers, and the Jack Support is removed.