W = nominal 12", 3/4" thick stock
Angles/tilts are 5 deg. Floor is 1.5"x8"x8" recessed 1/4" or more. Use 3/4"x8"x8" floor for a deeper box. A stove pipe predator guard
(invented by Ron Kingston) is recommended, use 8" dia. by 2' galvanized stove pipe. Place stove pipe right under the box. For plans
and article by Ron, see http://audubon-omaha.org/bbbox/nabs/rk1.htm.
Note: two entrance holes, 1.5" diameter. Grooves inside, 3/4" apart under holes.
Attach sides with glue and screws to the back, top, and floor. Only the front is allowed to be removable, hence not glued. Use SS screws or deck screws. Make sure all joints are sealed tight. View on the lower right is a cross-sectional view, roof is shown dashed.