My first 4x5 camera does not have a grid on the groundglass. I solved this problem by making my own. I used a processed sheet of blank film. (quite easy to do-often requiring no thought at all) My trimmer has a 1/2" grid pattern. A piece of graph paper would also work. I taped the film to the pattern and traced it with a fine tip felt tip marker and ruler. I carry it in a printfile 4x5 negative sleeve with a piece of white cardboard from a film box as a stiffener. Just hold it over the groundglass to use. I like the spacing of the 1/2 inch grid. Other possible applications include masks for 5x7 or other proportioned prints or rollfilm backs.