Last week we looked at the Multiple Extrude Command, very useful if you know the sizes, in plan, of the top and bottom of a truncated object. What if you know the angle you need and the size of the top OR the bottom?
I often se Tapered Extrude to make a simple backdrop. I set the height as required and the taper to 0 to create a 3D form I can texture from a 2D line. Of course, I can also use the Softgoods object. Always many ways to skin a cat.