Here is the bottom to show the chambers.
It was cut out of the extra from the 1/2" plywood used for the divider. I attached it using polyurethane glue so it will be water tight and painted it to be noticeable. Not that the bats will be impressed, but when friends see it they will not ask, "why that big box on the pole?" At this point I applied the first of three coats of polyurethane.
These are not to be bent until the piece is dry fitted to the bat house. Also there are 4 small circles containing "x" that represent approximately where the holes will be drilled once you dry fit this to the house. The solid lines are where you cut with scissors, and the broken lines are where you will bend the metal.
Here it is fitted and ready.
Finally I ran a very generous bead of caulk just under the metal top where it touches the front of the box. This will also help keep out unwanted pest.