To aid in orientation of a hodoscope system using a rectangular magnet with a uniform field, projections of the trajectory of particles in the horizontal and ventical planes are calculated approximately. Fringing field effects are represented by adding a correction to the length of the magnet and assuming the field to be uniform over the total effective length. The assumption that the source lies in the median plane of the magnet is also used in treating the vertical motion. (D.C.W.)