Particular pitches and prospects of the worm do not enable the worm equipment to drive the worm. This is valuable when the software demands to lock the output if the software is running in the reverse route. When the helix angle is much less than 5°, the worm is self-locking. When the helix angle is increased than 10°, the worm can be pushed back. Worm and worm gear assemblies need to be mounted on vertical, non-intersecting shafts.