Keyed(Anti-rotation) jacks
For machine screw jacks-A key, fixed to the jack housing and inserted into a keyway milled into the length of the lifting screw forces the lifting screw to translate without rotating( The keyway in the screw causes greater than normal wear on the internal drive sleeve).For ball screw jacks-Anti-rotation is accomplished by a square guide attached to the screw translating inside a square stem cover attached to the jack.