2,490. An Imperfection on One Side of the Knife

Hilchos Shechita 1:15

If a groove is on just one side of a knife, one may not slaughter with it. If one did so using the unblemished side, the shechita is valid after the fact.

Hilchos Shechita 1:16

Pursuant to the previous halacha, let’s say that a shochet checked a knife by running his hand over it and he didn’t feel any imperfections but when he drew it back, he felt it. If he slaughtered by moving the knife forward and not drawing it back, the shechita is valid; if he drew it back, the shechita is invalid.