1, draw a straight line with the back neck length, front neck length and door length (about 2 cm).

2. The rightmost point (the point where the door is built) drops about 1.2 cm, and draw an arc with a goose head ruler.

It is a smooth arc from this point to the point in the middle of the front neck crane's back neck.

3. Draw the height of the collar, about 5 cm, and draw a semicircle for the height of the right collar.

This is a kind of collar, some of which are very three-dimensional, that is, a small dart of about 0.5 cm can be opened between the front collar and the back collar.

Not very clear, for reference.