Measure your dog’s longest stride. Roll him on his side and stretch his front and back legs out, without hurting him, and measure the distance. Add 20 per cent to this; this will be the length of the running board. Measure his width across the chest while when he is standing; the running board should be 1 1/2 times this measurement. Measure the distance from the floor to the top of his head and add at least 5 inches; this will be the height of the frame. Record these three measurements.