My mat is the same, Bibliostone. I was warned early by one of my class teachers never to use mats for any precision measuring. I'll bet you that almost everyone will discover their cutting mats don't match their acrylic rulers. So always measure everything with your acrylic squares. Mats are unreliable.
Originally Posted by
bibliostone
Grrr, I am so frustrated! Today I discovered that the measurements on my mat are not the same as my ruler. I always cut with the rulers, but use the mat to make sure my blocks are coming out at 12.5 inches. Looks like I am going to have to rip and restitch some of the blocks I made because they are too small. I hope the blocks I sent out in the last boom were not too small to be used. This "redoing" was not included on my timeline!