Abstract: A template is provided for marking a picture mat blank in preparation for subsequent cutting. The template is comprised of two planar arms, a mat-opening design cut into the re-entrant corner of the arms, and graduation lines on the arms for measuring the widths of the mat borders. The template is placed in position on the back of a mat blank so that the arms are parallel with the edges of the mat blank and the edges of the mat blank line up with the appropriate graduation lines for the border widths desired. The inside edge of the template is then traced onto the mat blank with a pencil. Layout marks which show users of mat cutting machines where to start and stop cutting may also be traced. In addition, mat-opening designs incorporating cut out circles and ovals in the mat blank may be laid out using the template.