For many years I cut mats to fit the image. A Dexter mat cutter worked well with a T-square, although a Logan 4000 is easier to master and use. Laying out the cuts on the back of the window mat is quick with a series of templates made of scrap mat board with a strip mounted beneath to position the template's guiding edge at the right distance from the mat's edge. A self-healing cutting surface is unnecessary. Using any solid cardboard works well if it is shifted slightly between cuts to present a fresh uncut surface beneath the mat board. It is more practical to crop the image to fit some particular aspect ratio and size of mat. This also makes a more coherent exhibit. Pre-cut mats from a site like Frame Destination then becomes more economical, as does swapping prints between standardized mats.
