Following the click, the measured value of 120 mm displays in the Distance field and the Contour Flange previews as 120 mm long.
The sheet metal Contour Flange is the base feature in the model file that you created working within the assembly context. The sheet metal part displays as solid while the other components within the assembly display as translucent. By working within the assembly context you were able to use existing critical dimensions without initially knowing their values. Next, you add a sheet metal Flange feature with automatic mitering around three edges along the back side of the guard.