Final answer:
The "cutout" on a conventionally framed rafter that rests on the top plate is called a bird mouth.
Step-by-step explanation:
The "cutout" on a conventionally framed rafter that rests on the top plate is called a bird mouth. It is a triangular notch that allows the rafter to sit securely on the top plate while maintaining a plumb angle.
The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for food, courtship, and feeding young.
This cut allows the rafter to sit flatly and securely on a wall top plate, ensuring the stability of the roofing structure. Essentially, it's like a little notch or “mouth” that helps the rafter to have a better grip and alignment.
Ornithologists tend to use the word “bill” more often than “beak.” Some people use “beak” when referring to songbirds with pointed bills, and “bill” when discussing birds like ducks with more fleshy beaks. However, both words are used in reference to a wide variety of species.