No Nicks [פגימות ]
6. The shechita knife must be completely smooth, without any nicks along its entire length. The reason is because the Torah requires us to shecht the simanim, and if the knife has a nick, it punctures and tears the simanim rather than shechting them (חולין י . ו רשי ד"ה נפגמה, שמל "ח ריש סי' יח ). An animal shechted with a nicked knife is a neveila.
Size of the Nick
7. Catches the fingernail. Some say an indentation is considered a nick if it catches the fingernail, i.e., when one runs the end of his nail over it, part of the nail is caught by the nick and goes into it somewhat (רא"ש לפי הטור סי' י"ח והשו"ע הרב סי' י"ח סק"ג, רש"י בכורות ל ז'' .).
8. Single hair. Some are more machmir and hold even if a hairlike strand is caught and goes into the nick, the knife is posul (הרשב"א בתוה"א דף י"ג, ר"ן בשם הרמב"ן, ב"י בשם הרמב"ם ). The Shulchan Aruch paskens this way (יו"ד סי' י"ח ס"ב ), and some Acharonim also agree with this (מהרש"ל סי' ל"ח, ש"ך סק"ד, דע"ת סק"א, ערוך השלחן סי"ג ).
9. Feeling. Some are even more machmir and hold that the knife is posul even if one merely can feel the nick, i.e., he can sense something there when he runs the end of his nail over it even though no part of the nail enters it at all and nothing gets caught on it (ר א"ה בדק הבית, דרישה ופר"ח ס"ה בדעת הרא"ש, פמ"ג משב"ז סק"ב ).
10. Not smooth; “שיבולת ”; rough; “krechtz.” Sometimes, a shechita knife is sharp and has no nicks, but it is also not totally smooth; it has the texture of the top of a stalk of grain [שיבולת ] and creates friction against the fingernail. In other words, one’s finger does not glide smoothly over it; he feels he needs to push his finger more than he does over a smooth knife, but it does not actually have a nick.
11. The Mechaber writes that one can shecht with such a knife (שו"ע סי' י"ח ס"ו ), implying this is even true l’chatchila (כנ ה"ג בהג' ב"י סקט"ז ).
12. However, the Rama writes we do not shecht with it since we are not proficient in the matter (רמ"א שם ). Some write that even Sephardim are machmir not to shecht with it (זבחי צדק סקט"ז ).
13. Some say that if one shechted with it, the shechita is kosher b’dieved (תבואות שור, הגר"ז בדעת הרמ"א, שמל "ח סקי"ג ). Others say one should even be machmir b’dieved (פרי תואר סק"ג וסק"י, דעת קדושים סק"ב ).
