Hello,

I am repairing a small section of my three-tab composite roof, and
installing a ducted roof vent for my bathroom fan.

What is puzzling me is that in addition to the two holes at the top of the
roof vent (which will be covered by the top course of shingles), there are
also two holes at the bottom of the roof vent.

If I put nails into these holes, they will be exposed, which is something
that I know should be avoided.

Here is a picture of the roof vent:

http://jonnycats.home.comcast.net/~j...s/RoofVent.jpg

I'm hoping that the people who make the roof vent know what they are doing,
but what exactly am I supposed to do here?

I'm guessing I am supposed to run the lower course of shingles to where they
are butting into the left and right hand side of the section of the vent
that rises up from the bottom plate (flange), so that the nail/nail holes
are covered by them.

In other words, should the shingles (represented by the mustard colored
overlay) cover the flange as in this picture?:

http://jonnycats.home.comcast.net/~j...RoofVent03.jpg

In all of the other roof vents that I have seen, the entire width of the
bottom end of the vent flange is treated like a shingle, and is just left
exposed without any holes or exposed nails, which is why this configuration
is puzzling me.

Thanks for any help on this,

Jon