Laid out a 2 inch grid on a 4 foot square piece of 1/4" birch ply. This is for laying out and checking the curve of the rudder bow.
First I clamped my 48" straight edge along one edge of the plywood. Then I ran a carpenter's square along the straight edge and drew pencil lines every two inches. After doing all the lines in one direction, I rotated the plywood 90 degrees and repeated the process. Since the square didn't reach all the way across, I used the 48" straight edge to draw them to the other edge of the plywood.