|Figure sketch with Prismacolor Stick|
For technical drawings, if you colored in a pair of lines making a wall thickness on the back of the drawing sheet, especially with orange Prismacolor color, and blended it with a tiny drop of lighter fluid on a tissue, you would get a beautifully shaded wall on the final print (Ozalid reproduction). Doing the shading on the back allowed for trimming areas or errors with an eraser and an erasing shield without messing up the original line work on the other side of the sheet. Of course, hand drafting is rapidly vanishing by the replacement of CAD computer drawings. I admit that I also got a CAD system for my architectural office in 1989. But, I still sketch and do simple cabinet and furniture layouts by hand.