Nestboxes

What do you think is the narrowest nestbox you think you can use for widowhood, A fella at our club says his boxes are 20 inches wide and 2ft deep.

depends on the type of box

just a square with nestbowl at the back, and a lift up dowel front

20 inch is fine as you can still get 2 bowls in them and i would say 20 deep aswell then you could have a front set back to enable a perch at the front of the box for widowers

his are 24 inches deep, they looked narrow to me, he swears by them

make them double fronted
have a 14 inch square box then 28 in deep put front at 14 inch deep then put it so front can be put at front of box to make a full size box