US Patent 7887443 Frame for measuring pitcher's circle

A frame for measuring a pitcher's circle includes a housing for engagement with a pitcher's plate, a measuring line and a guide rod. The measuring line is swivel connected to a centering member on the housing, with its free end connected to the guide rod. The measuring line has a predetermined length such that the tip of the guide rod represents the radial distance of the pitcher's circle when the measuring line is fully extended from the centering member. The pitcher's circle is marked out by simply walking the guide rod about the pitcher's plate. A leveling member is provided on the guide rod to ensure that the guide rod is kept at 90° vertical to prevent measuring inaccuracies.