Aunt Norie’s Sewing Room
You've probably more than once folded a handkerchief, napkin or even a washcloth (after) laundering, only to find the corners are far from even and it won't fold up squarely at all. It may have been or appeared to have been perfectly square.
Then you washed it and in doing so, removed all of the sizing in the fabric. Then it reverted back to its true shape -- it will always be "off grain." Yep, that's it in a nutshell.
That's why we need to be sure our fabric is straight before we cut it because after it is laundered the very first time, if it's a dress or skirt for instance, if it is not cut on grain (we call it) it will never hang straight and nothing you can do will help.
Check those thread ends right there in the store before the sales clerk cuts your fabric. If its ends are not square, point it out to her and ask her to allow you enough to straighten it. An experienced clerk in a regular fabric shop will probably catch it before you do.
To straighten your fabric when the ends are uneven, pull a thread (easing the fabric back onto the thread you are pulling). It will leave a puckered line. Cut along that line from selvedge to selvedge.
Some fabrics can be torn. Make a cut into the selvedge, then tear it on across that torn line so it will be straight. A stripe or plaid or rib in the fabric can be cut along a prominent thread from selvedge to selvedge.
Fold the fabric in half lengthwise with selvedges matching the crosswise ends. This should be at right angles with the selvedge, if the fabric ends do not match, remember now it is straight but has become stretched and twisted on the bolt. You just need to stretch and pull it back into shape, you can easily do this by pulling and stretching on the true bias, in the direction opposite to the grain threads. Start at one end, continue pulling along the length to the fabric until those ends are even. I know it sounds like a terrific job -- just do it once and you'll see how easy and worthwhile it is.
Good luck now, until next week, God Bless.
-- Aunt Norie, P.O.Box 265, Tonganoxie 66086, firstname.lastname@example.org.