3mirrors Engine Air Valve Holder Pressure Pipe M14+M18 Thread to 1/4 NPT with Ball Valve, Cylinder Leakage Testing Assistant Tool Compatible with Mustang Ford GM Trucks LS1/LS2/LS3/4.8/5.3/6.0. Place the Bottom Aluminum plate on the head where the rocker bolts mounted and place the middle section on top that has the stud and mount it to the head with the 2 supplied bolts make sure the tool is setting in the middle between the 2 valve springs.