Our canvas laces inside the frame, so every measurement goes inside face to inside face, to the nearest quarter inch, with a steel tape and a helper. Take five: front to back down the centerline, side to side at the front bar, side to side at the rear bar, and both diagonals. Photograph every light, antenna and rod holder, and send it all with your boat's make, model and year. Do not cut the old top off first: it is the pattern.