birdsmouth UK /ˈbɜːdsmaʊθ/US /ˈbɝdsmaʊθ/noun 1verb 1forms 3 noun1 •A notch cut into the underside of a rafter to ensure that it does not move when resting on the wall plate running across the top of a wall; a similar notch in other timber components.After the wall and ceiling framing has been completed the erection of the roof takes place. Nail the four straight rafters selected as the first and last into position at the birdsmouth. — 1995 verb1 •To cut a birdsmouth into a rafter or similar timber component.The end of the common rafter is birdsmouthed and nailed to the pole plate. — 1895 formsbirdsmouthed · birdsmouthing · birdsmouths
