Originally Posted by mrs. fitz
I went back and looked at the picture and sure enough, I used to have one when I made a lot of my clothing. I think it was a large portable surface for laying out and pinning fabric and patterns which folded into nothing when not in use. I think (think being the key word) pattern pieces could be lined up accurately for placement of darts, etc. by using the marked lines.
I agree; it looks like a portable area for cutting out patterns. I used one for years when sewing. I either used it on top of my dining table to protect the surface or on the carpet so I wouldn't cut the fibers and/or pin the pattern to the carpet.