from the GNU version of the Collaborative International Dictionary of English
- n. An interior angle or notch cut across a piece of timber, for the reception of the edge of another, as that in a rafter to be laid on a plate; -- commonly called crow's-foot in the United States.
from The Century Dictionary and Cyclopedia
- n. In carpentry, an interior angle or notch cut across the grain at the extremity of a piece of timber, for its reception on the edge of another piece.
Sorry, no etymologies found.
If the logs are squared, cut a small bird's-mouth notch in the rafter where it extends over the side-plate logs of the pen and bevel the top end of your gable rafters to fit against the ridge-pole as in the diagrams.