Well not that I can see. Looks like you just turn a key from inside the cab, depending where the unit is affixed, to isolate the clutch supply fluid, so clutch is inoperable. You could leave the engine running unattended in certain situations (not that anybody would usually), then if someone jumped in to drive off, the clutch wouldn't work. Once you unlock with the key, then the supply is re-connected. I think that's how it works.