2,487. Cutting the Trachea and the Esophagus

Hilchos Shechita 1:9

The shochet must slaughter in the middle of the neck but if he slaughtered to the side, it’s valid. The measure of shechita is that one cut the two signs, i.e., the trachea and the esophagus. The best shechita cuts both of these, both in animals and in birds, and a shochet should intend for this, but if he cut the greater part of one in a bird or the greater part of both in an animal, the shechita is valid.

Hilchos Shechita 1:10

If someone cut one sign completely plus half of the other sign in an animal, the shechita is invalid. If he cut the greater part of both, the shechita is valid even if he only cuts a hairbreadth more than half. If he cuts even the smallest amount over half, he has cut the greater part.