From one picket:

• Front and back: 9" long, with a peak cut at 45° on one end of each
• 2 sides at 6"
• Floor at 4 1/4"
• 2 roof pieces: 7" and 6 3/8" (one overlaps the other at the ridge)

Bore the entry hole in the front piece, centered, about 6 1/2" up from the bottom: 1 1/8" for wrens, 1 1/4" for chickadees. Resist the urge to add a perch — the birds don't want one.

Glue and nail the sides between the front and back, then fit the floor recessed 1/4" up from the bottom edges (keeps rain from wicking in). Snip the floor's corners off first — instant drainage holes.

Nail on the two roof pieces with the longer one overlapping the shorter at the peak. If you want to clean the box out each spring (the birds appreciate it), hinge one roof half instead of nailing it.

Drill two 1/4" vent holes high in each side under the roof overhang. Leave cedar unfinished — paint and birds don't mix. Hang it 5–10 feet up, away from feeders, hole facing away from prevailing weather. Then be patient: houses often get tenants in their second season.