Particular pitches and qualified prospects of the worm do not let the worm gear to push the worm. This is beneficial when the application wants to lock the output if the application is managing in the reverse route. When the helix angle is much less than 5°, the worm is self-locking. When the helix angle is greater than 10°, the worm can be pushed back. Worm and worm gear assemblies must be mounted on vertical, non-intersecting shafts.