Abstract: A pair of generally rectangular core box mounting plates are cast from aluminum. Each plate includes a plurality of parallel spaced ribs extending outwardly from a surface of the plate to define channels therebetween permitting excape of compressed air and sand from core boxes positioned between a pair of such plates. Extending along and sealing one edge of the channels is a ridge which directs the sand, air and gases from the core box to the open ends of the channels. Mounting flanges are provided such that the structure consisting of the core box mounted to the plates can in turn be secured to a shell core machine. In order to accommodate relatively small core boxes, a plurality of the ribs are shortened to provide lands which can accommodate spacer blocks so that a pair of universal plates can be used for different sized core boxes.