When I started using the mats and rotary cutters, the board didn't have lines...now when I get a board that does, I don't use them. I use the lines on the ruler. Much more accurate.

As the self healing mats get older, they do "dry out" Then you might have a problem. I was told to soak mine in water, then dry it off, lay it on a towel and allow to air dry. Never lay it in the sun though. It worked! Great way to re-new your cutting mats. Helps with the self healing.

nah, there are no "shoulds" if you are happy with the results.

I say to use whatever technique works for you. However, it is a good idea to square up as you piece. That way you will know two things: 1) that your cutting is accurate; and 2) that your sewing is accurate.

The main reason why a ruler is more accurate is because of the size of the marks on the mat - they are much thicker than on the ruler. As many others have said, if you are consistent in the way you cut and you have experienced no problems, why change. When you do use the mat, try to be consistent in where you put the ruler - left side of the mat line, right side or center.

I double ruler my cross grain cuts and almost never use the cutting grids. I use a 12 1/2" square ruler along the fold and the 24" long ruler to lay across the fabric to cut. If the lines on the two rules line up with the folded edge I know the cut will be right. That is of course after I fold the material straight.

I do use the angle markings for cutting 45 and 60 degrees. But I always do the double ruler with that too.
peace

I too was told a ruler is more accurate than the mat when I first took a class. But I use my ruler instead of the matt for the following reasons:
1. I am not constantly cutting on the same line thereby wearing out my matt on an often used measurement like 2" or 2 1/2".
2. I am not limited to cutting in a certain direction or position by using the ruler instead of the mat.
3. Can't imagine cutting a 1/8" measurment using the mat/
4. Rulers are much more portable than mats, especially if you have a big mat. It is best practice to always use the same measuring tool when working on a project so I can cut at my machine or at my cutting table by using my ruler.

I use them also. However I am also left handed. I place the material on the line, the ruler on the material and cut it with my left hand. It works for me.
But I have noticed that the lines are becoming permanent after many years of using only the lines to orient the cuts. Even after I clean the mats the lines are still there. The self cleaning green mats are not as damaged as my large 68 x48 white commercial mat.
MaryKatherine

I would stick to whatever works for you...Women didn't have cutting mats, rotary cutters etc back in the day..you don't hear that they did it wrong do you...LOL...

lol well I use mine too, and what else would you use. its there and I cannot imagine a reason not to use it.