Certain pitches and prospects of the worm do not let the worm gear to push the worm. This is beneficial when the application needs to lock the output if the software is working in the reverse direction. When the helix angle is considerably less than 5°, the worm is self-locking. When the helix angle is greater than 10°, the worm can be driven back again. Worm and worm gear assemblies have to be mounted on vertical, non-intersecting shafts.