KD Indexing Ball Joint Separator 15/16" Opening 3990 Recommended use of only 0, 20, -20 Degrees positions when in use for manual or pneumatic striking mode. Can also use in 90 degree position when striking the manual hammer surface. Indexing feature allows for access in tight areas. Manual hammer position keeps your hand safely out of the way when using tool, so you can swing harder without fear. To use, insert 15/16" opening between parts and strike with hammer. Seperator is forged to withstand hard useage. #10