I worked on a door in the top cowl to access the oil dipstick. I located the dipstick using a plumb bob and then transferred the location to the surface of the top cowl. I cut a hole in the cowl and then fabricated a frame from .040 aluminum on which the door will close. I cut a small section of piano hinge. I then cut a door from .040 aluminum and bent the door to fit the shape of the cowl.