Double sizes

Dear users, dear designers,
what are double sizes needed for, and how can you then adjust the model to your own size?

Double sizes are useful when you’re stuck between standard sizes—for example, if a size 42 is too small but a size 44 is still too big. If I have a pattern size in a sewing pattern that’s too big for me, I cut it without seam allowance, and then it fits again.
I worked in the clothing industry for a long time, and there were times when we’d run out of size labels for, say, size 38. Then we’d check what else was available—size 36 or 40—and sew those in instead. That also explains why a size 36 might fit you even though you’re a size 38 :-) But that’s how it was done whenever a size was missing—we’d either sew in the next larger or smaller size, or just use a double size label.

That’s funny! I didn’t know that people were “cheating” like that either. But now some things are becoming clear to me:

By the way, double sizes really do make sense for loose-fitting or stretchy garments, because an intermediate size actually fits both standard sizes.