Speed was controlled by means of a throttle valve lever. The mount has a castle nut that screws into the bottom of the locking lever. A steering column-mounted gear lever was fitted. Drivers can manually select gears using either paddles or an electronic gear selector lever. The "lock" refers to the release mechanism, including the string, sears, trigger lever, and housing. When engaged, the safety lever blocks trigger movement. The clutch had to be depressed every time the gear shift lever was moved. The external safety is a small inner lever contained in the trigger. The gearshift lever of an underbone has two ends. The throwing arm together with the atlatl acts as a lever. There is no clutch lever on this model. The floor selector lever also has an S position. I go in there and pull the lever. This early arquebus was a hand cannon with a serpentine lever to hold matches. Archimedes discovered the principle of mechanical advantage in the lever.