by the nape of (one's)/its/the neck
By the back of the neck (of a person or animal). My mom was so mad that she grabbed me by the nape of the neck and hauled me into my room to be grounded. I had to yank the cat out from under the floorboards by the nape of its neck. The boss took John by the nape of his neck and warned him never to do something so foolish again.
by the nape of the neck
by the back of the neck. (Mostly said in threats.) He grabbed me by the nape of the neck and told me not to turn around if I valued my life. I stood very still. If you do that again, I'll pick you up by the nape of the neck and throw you out the door.