I think I figured this out. So here is a tutorial.

This ruler was given to me. It is a Short Cut made by Jun Tailor. I have tried using it before and found out I don't have enough strength in my off hand to keep it from sliding. 

I would like to use it for multi-cutting off of one fabric. So my Husband and I worked on the process. I set it on top of the table in my sewing room. I used my mat on the hard side of my ironing board by June Tailor. No affiliation. 

I can successfully cut through 4 layers with a new blade in my Rotary Cutter. I place the fold on one of the graph lines on the edge of cutting mat.  

Now the ruler is place and matching lines for being square. See how it overhangs the ironing board and the mat is on the fabric to make a square cut. This is where my troubles can in. I am right handed, but start on a left handed way of cutting. I hand sew that way also. I had a sewing teacher tell me I hand sewed backwards. It is just what works for me. 

Here comes the solution. I had some clamps that we saved off of some plastic hangers and it clamps the mat, fabric and the ruler secure enough to make good cuts. It is and extra step, but it works. The ruler was sliding and I was getting wonky cuts. Now they are perfect. This ruler cuts in 1/2 inch increments so you can get a lot of mileage out of it. On You Tube there is several videos of the use of this ruler. If my directions are clear as mud you can check out the videos. 

I used the smaller cutter, but I struggled to get it up high enough to cut between the slats. I changed yo a 45mm cutter and it worked much clear. But remember to use a new blade. 

Here are the cuts I made off of that piece. As I said 4 layers is about all you can cut with out slippage. If you have one of these rulers in the back of the closet and you figured you made a bad buy try it again. 

Stopped to eat lunch and then back at it. Chris