The V-groove is a simple technique used to add interest to a mat. Its primary function is to break up space in a broad, plain-coloured border. It should be added before the window is cut.

In a three-inch border a V-groove may be most effective when cut one or two inches from the outer edge of the mount.  This gives a pleasantly asymmetric feel to the design and draws the eye to the mounted image. The V-groove itself is normally no more than 1/8" wide, a measurement determined by a standard setting on many mount cutters.