Foot levers are usually located at the right hand end of the pedalboard, above the toe pistons, on many Christie and Wurlitzer organs.
Their function varies, but usually includes a drum roll/crash function (using second touch) and a sforzando function, bringing on all the stops together or progressively.
Larger Wurlitzers also had foot levers for bringing on diaphone or tuba bass pipes in imitation of thunder. History does not relate how the silent picture organist was to distinguish between the need for diaphonic or tuboid thunder from the images on the silver screen.