I am trying to follow a book on using blender (Blender 3d by Example), however I cannot seem to achieve the same result when following the steps exactly. What I want to end up with is the picture below. I have a skewed cube, with one face extruded and then scaled down but only parallel to the skewed side. The book however, uses the S + Z key combo for this. But this essentially moves the top and bottom edge up and down in a straight line.So I want the scaling to happen as in the example below. Please note that in the example image, I've tried to achieve the same by extruding first and then moving the edges into their skewed position. But this seems cumbersome. In real situations, the object I'm working on may have been skewed already. Any help would be appreciated!