Abstract: A paper mask produces even width borders on bordered photographic prints even if the unexposed photographic print paper is misaligned, angularly mistracking, or wandering in alignment through roll feeding, or if the width of the paper varies. The paper mask apparatus includes a base which is mounted on the paper deck of the printer and front and rear guides which are movably mounted to the base and have masking lips which overhang the longitudinal edges of the print paper. The front and rear guides are generally parallel to one another and are urged toward one another by bias springs. A separate masking frame of the desired print size is mounted to one of the two guides and moves with that guide to define transverse masking edges.