The 6.5″ small Gammon Reel is used to suspend a plumb bob under a surveying instrument. It can also be used to suspend a plumb bob while providing a target to accurately position with a surveying instrument. Use the 6.5′ small Gammon reel as an aid to set up and deploy a clean, accurate plumb. Slip the reel into your palm and draw the bob to desired position and stop with finger pressure. Steel clock spring zips the string back into the case.