Starrett CH604R-6 6 2-Sided Steel Ruler with Hook
Starrett 6" x 3/4" x 0.043" ruler with hook permits accurate measurements even when the user cannot see if the ruler is even with the measuring edge.  Useful for measuring around corners, through hubs, for setting inside calipers, etc.  Hook may be reversed or removed.  Flush starts on both sides.  Spring tempered steel with satin chrome finish.