Certain pitches and leads of the worm do not allow the worm equipment to travel the worm. This is useful when the software wants to lock the output if the application is running in the reverse path. When the helix angle is significantly less than 5°, the worm is self-locking. When the helix angle is higher than 10°, the worm can be pushed again. Worm and worm gear assemblies need to be mounted on vertical, non-intersecting shafts.