Abstract: A template for marking batters' and catcher's boxes of a ball diamond in conformance with league or other standard regulations. Included is a rectangular frame with dimensions having a preselected relationship to the two types of boxes, an index arm for positioning the frame relative to a home plate for marking a batters' box, and indicia on the frame for locating a catcher's box relative to the previously marked batters' box. Optionally, the frame and index arm dimensions are adjustable, and plural sets of indicia are provided for marking the two types of boxes in conformance with different standard regulations. Additionally, the template may be collapsible for reducing it into a more compact unit.