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I want to create a sharp edge between two smooth mesh surfaces. The upper surface has already been smoothed out nicely, merely using the Shading/UVs > Smooth Face function in the Tool Box (top left of picture), after selecting all its faces. However, when I do the same thing in the lower surface, the common edge between the two surfaces (= top edge of selected faces in picture) is also smoothed out (the picture is before that operation), which I don't want. I tried Shading/UVs => Smooth Edge=> Sharp, but that does not work. I don't want to use a modifier (because I want to control things intra object).