I just purchased another large Olfa mat and butted it up against an existing mat withDritz double sided Res-Q Tape. My older mat has been taped down with the double sided tape for over a year and has never moved even a fraction of a smidgeon. In other words, the tape is good stuff! I secured several rolled pieces of the tape along the edge that butts up against the old mat. Fits exactly perfect and measuring the inch marking along the bottom, it is a perfect inch spacing. Lines up beautifully. I can't believe I waited as long as I did to make a bigger mat. No more moving yardages of fabric while cutting. There is no lumpiness or raising of the mats using this tape. This tape can be found most anyplace.