I have the same problem so I am of no help. I will be looking
for the answer too.

When I started quilting, I was told that squaring up your fabric will only be accurate for the width of the ruler you used. If you use a 6" ruler, you should square your fabric every 6". But I still have trouble. I can't double fold the fabric or I'm doomed.

Yes, the secret is to line up the ruler with the fold, then cut down the side to straighten the material, and each time you want to cut a strip, do the same thing and also don't move the fabric, if you move the fabric you have to line up the ruler with the fold again and again and again... you soon learn the hard way... it isn't hard, it is just knowing what to do...

Also only fold the material over once... not worth the risk folding it over twice... only takes a few minutes extra to do the fold over once and cut on each strip... more accurate that way...

David, I think it moves if you have more than two thicknesses of material. I know it it slower, but I stick to only two or three thicknesses and never have a problem - any more than that, and there is movement. We don't have the starch trend here as much as you seem to do it in the 'States, so that could help,I suppose.

I found this on youtube hope it helps.

http://www.youtube.com/watch?v=C_eue...eature=related

When you cut in with it folded you will get a dip in it have to cut it single layer

... just one more suggestion - make sure your fabric is straight of grain .. if the fold is slightly off, has kind of a kink or wrinkle when you hold it up by the cut edge, you will not get a straight strip.
If it's looking kind of iffy - iron out that center fold line, hold it up again and sort of shuffle the fabric if needed so the 2 selvedge edges line up... you can then actually fold it 2 times and still get nice straight strips - but practice on a few before you do that :)

I did the same thing on nearly everything I cut until I tried putting 'gripper dots' on the back of my rulers. While cutting, the ruler can shift as you cut away from you, especially if you don't stop midway, and move your hands carefully. I now have 'dots' on all my rulers and templates. MUCH more accurate cutting. I hope this will help you too!

* I also use sizing to iron before I cut. It seems to keep everything lined up better for me than starch did. Individual preference I'm sure, but hey try anything, right? :D

GaiGai gave excellent illustrations. Many quilters match up the selvedges and then cut. The selvedge is not important, but the fold is. If you cut straight from the fold, it does not matter that the selvedge does not line up.

Starch is your friend.

Sandpaper on the back of your ruler is helpful. Use an office supply cheapo punch, fine sandpaper & glue on with rubber cement. If all else fails, just use the rubber cement!