Abstract: A device for making miter cuts in workpieces includes a saw guide pivoted to either a bottom surface B or a top surface A of a board. The saw guide includes two plates spaced above the board surfaces by a pivot assembly and a swing assembly. Almost any commercially available circular power saw may be accommodated by placing the saw base on the plates, positioning the saw blade within alignment slots in the assemblies, and adjusting rails on the plates against the saw base. A keeper on one of the rails prevents the saw from jumping out of the saw guide. When the rails are properly adjusted, the circular saw blade will travel along a saw line between the plates from alignment slot to alignment slot. The top surface A of the board has a straight edged backup adjacent a planar work area. 90.degree. and 45.degree. stops on the top surface reliably and accurately position the saw line normal to or at a 45.degree. angle to the straight edge and aligned with 90.degree. and 45.degree. slots in the backup.