I needed to use an old megarocket bat house top/roof I had lying around for years so I added one more layer/box to my usual design with it now being wider than 12". I used the boards horizontally and it worked out well for fitting the old top/roof. I figured I'd leave a horizontal opening for a potential additional bat access as well. Hope to get this up next spring but meanwhile I'll use it and the stand for presentations at local schools and for unattended educational presentations.
Great looking house Joe! I have yet to try a rocket style house but incorporated a "wrap-around" chamber to my nursery house similar to the rocket's 360 degree chambers. By adding another chamber to your original design, I think it should be much more attractive to bats and definately house a greater colony. I am most interested in seeing if the bats use the horizontal slot as an entrance/exit.
Now we just have to wait untill spring when it is put up!
