Knife tool issue

Okay im trying to make a face on a turkey im modeling so i tried using the knife tool but i cant get it to cut the shape that i want for the beak, (a triangle, which is the top half of the beak. i wanted to know if there was a way to use a shape to cut out exactly those lines, like i’d put a triangle over the head and somehow blender will cut in the head exactly on those lines. i hope i’m being clear. thank you!