Wheelnut,

In the first pic, you can see the chamber and the flood holes

http://s179.photobucket.com/albums/w...rPlacement.jpg

In the second pic, you can see it from the transom.

http://s179.photobucket.com/albums/w...nt-Transom.jpg

The hatch was designed a little taller, in order to facilitate a quicker turn over.

Duck