adjustable cylinder head stand
Fasten the stand in a vise and screw it up the thread The valve heads are different in diameter size, so to be able to hold the 2 valves,
so that they cannot move whilst you are doing your repairs, the big nut is welded
to the flat plate off centre from the securing screw threads.[the 8mm long ones]
Mount the head onto the tool, the correct way round, secure it with the 2 x 8mm nuts and then screw the head downward until the big bolt touches both valve heads. The valves are now locked in position and cannot move. This tool is also handy for when you are putting all the valve components together. It's another pair of hands.