Particular pitches and sales opportunities of the worm do not allow the worm equipment to travel the worm. This is beneficial when the application wants to lock the output if the application 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 better than 10°, the worm can be driven back again. Worm and worm gear assemblies should be mounted on vertical, non-intersecting shafts.