shape of the opening. The apron of the flange may now be drawn around the opening, allowing at least 3 in. on the sides and
![](//upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Smd_d144_roof_flanges.png/450px-Smd_d144_roof_flanges.png)
Figs. 176-181.—Roof Flanges.
and 6 in. on the top. A hem should be added to the long sides of the apron to direct the flow of water.