because it is easy to do crosswise than lengthwise
A fold is when an object, normally a flat and thin one, is bent and part of the object placed on top of the rest of it. You can fold paper, cloth, omelets, sheet metal, carpets, etc. etc.In...
No - that's why it's on the fold, so you end up with an extra-large piece and don't need to sew along the fold-line.
(geology) A fold in which the mechanism of folding, either flow or slip, crosses the boundaries of the strata at random.