Use the line level to determine the slope of the eaves on the short roof. The side that intersects the long roof is nearly level, so we snap two chalk lines: one to mark level elevation and one to mark a 1/4-inch drop to the end of the roof. The 1/4-inch drop denotes the mounting line, because all gutters must slope downward at least 1/4- inch for every 10 linear feet in order to drain properly. You will need to consider edge of the porch roof to determine placements of downspouts and types of corner joints.
