I can't begin to imagine cutting with the desired width entirely free of the ruler. That's how I square up the edges, but I would never cut useable pieces that way. There'd be no way to know if you were 'off' even minutely once you put blade to fabric. Do you have a link to the thread for that discussion?

I use a 24" long ruler, line the fabric fold up on the mat, line the ruler up perpendicular to the fold, walk my hand up the length as I cut, never cut more than 4 layers, and only have one fold in the fabric. My rulers are Olfa Frosted Advantage.

I cover the backs of my rulers with InvisiGRIP and when I really need my ruler to stay in position, I add a Gypsy Gripper. When squaring up yardage before cutting patches, I usually use a 6" x 24" ruler. The V that ends up in your strip has more to do with how square the fabric edges are, and less to do with your ruler slipping:

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I won't use a ruler without the Quilter's Slide Lock. It stops all ruler and fabric slippage but the main reason is the safety. I have the Alto Quilt Cut II and a Go die cut machine and the different sizes of June Taylor Strip cut rulers. I get the V more times then not with all of them except the Go.

My usual ruler is the 6" x 24" also, with the invisifilm to keep it from slipping. I find that I have to have at least one finger (usually my pinkie) NOT on the ruler, but on the cutting mat, to get more stability. I also walk my fingers up the ruler for longer cuts - ensuring that I'm not cutting where my hand is stabilizing the ruler.

Before having a bone removed from my wrist I purchased a ruler from Australia which has a black piece at the back which slides to the correct place and then tighten by two screws. I then. Put an old iron on top to keep still. Worked well. Also ruler makes cutting very accurate.

[QUOTE=Deb watkins;6747815]First of all, align the salvages and the folded edge so there aren't any wonky edges at the fold, then the 5 x 18 ruler works best for me when I cut.[/QUOTE

For me this is the most important step. If fabric is not align it won't cut straight. Before I put fabric on cutting mat I hold it up and play with it,move back & forth, until it lines up.

I've had fabric move the minute you put the ruler down on it. Lycra is very slippery, and I used a lot of it at one time. If I get totally annoyed with it, I use drafting tape to tape the fabric to the cutting mat same way as I did for Lycra. Drafting tape leaves no residue.

For a long time I could not understand why I always had a V when I cut folded material. My ruler was not straight. Got a new one, no more V's.

I make my first cut with the fabric folded only in half, with at least a 6 X 24 ruler lined up with the fold on the fabric so that anything on the right gets cut off. (I'm right handed.) Then I fold that in half again and turn it around so that the cut edge is on the left. Now I lay my ruler on the fabric the width I want to cut it. (Be sure to look up and down the entire length.)
Now I place my cutter about two to three inches above the bottom edge and cut back toward myself. This keeps that edge from getting distorted. Then continue the cut, moving the other hand as necessary with the cutting wheel held in place while you move.

I use a 24" x 6" ruler with grip strips. I only fold my fabric once as I use to get slight dog legs when I folded it more. For smaller pieces I have a 61/2" x 12" ruler with grip strips.