Originally Posted by MamaHen
Hold your fabric up-salvage to salvage, now move the front salvage piece left to right- right to left, until the fabric looks straight from side to side. If you see little waves in it, it is not straight. It takes a little practice, but it helps. I find that more than a yard or so is a bit much to hold. I also found that if I press out the middle fold, the fabric will fall straighter. Good luck.
This is critical. You really need to look and see. If in doubt then cut just a sliver off the material, open it up and check if it is straight.
ali