I am learning how to sew and have not yet graduated from stuff sacks yet, mostly because they're still kicking my ass! I've got some cheap wally-world uncoated ripstop, which I've laid out with a square, taped down, cut with a "hot knife" (solder iron), before I even get past step one and fold it in half the thing's gone all wonky on me and nothing is square anymore. I have not had this problem with cotton fabrics
So how do you keep this stuff from shifting?
Thanks.

RED

don't use any of the edges as square. Place the square inside the edge and use the square to draw a new "edge" line. Start off that line and be careful not to stretch the fabric.

However, a little off square is no problem. Once it is sewn up you won't even notice, and neither will anyone else. I never noticed until i started sewing how imperfect the things we buy are stitched.

-Tim

Thanks Tim I'll give that a shot, and you're right I'm sure the minute I'm done I won't pay much attention to the imperfections.

Good Luck
RED