Rob, I also remember that machine. You ran the fabric fold through to measure it, then kind of hit the top of it to start the cut. Except plaids, which I remember being cut single, right along the thread line.
Nonetheless, we still would pull a thread get the grain of the width, then checked to see if the warp and weft were perpendicular, then pulled it on grain if needed. And Mom made us out a new fold into the fabric if it wasn’t exactly in the middle.