I am attempting to contact print three 5X4 negatives together to form a single 5X12 image. I am content with my ability to align (or not) the images during the taking phase, and am fine with seeing the unexposed edges of the film in the printed image. However, I'm having difficulty holding the three sheets of film in alignment with each other as I engage the film and paper in the contact printing frame.

Does anyone know of a technique to hold the film perfectly abutted while clamping the glass on the film/paper?