Hi Lo Detector 16ft.  HM-418
Used for measuring pavement planeness.  Operated by one person along a highway, airport runway, or bridge surface.  The unit detects and dye-marks high and low areas that need to be ground or rerolled.  Variations are magnified 16 times on a vertical scale graduated in 1/8" increments up to 1/4".  Uses replaceable bright orange aerosol marking dye.  One case, (12) cans, comes with unit.  
16 ft. unit has aluminum reinforcing plates on both sides of the main beam for added support and rigidity.