Steel Protractor, Rectangular Head, Blade 6 Inch Arm with Lock Joint and Knurled Nut Allowing Securing Any Angle Firmly, Back Flat, Allows Use for Drafting, Graduations 0-180 Degrees In Opposite Directions Permit Reading Direct and Supplementary Angles, Finish Satin Chrome, Measure and Transfer Angles, Set Bevels, 4 Edge Reference