is rendered non-kosher. Iqqur can occur if one tears out the esophagus or trachea while handling an animal's neck or if the esophagus or trachea is torn by a knife with imperfection/s on the blade, such as nicks or serration. In order to avoid tearing, the kosher slaughter knife is expertly maintained and regularly checked with the shochet's fingernail to ensure that no nicks are present. Breaching any of these five rules renders the animal nevelah; the animal is regarded in Jewish law as if it were carrion. Temple Grandin has observed that "if the rules (of the five forbidden techniques) are disobeyed, the animal will struggle. If these rules are obeyed, the animal has little reaction." The knife The knife used for shechita is called a sakin (), or alternatively a chalaf () by Ashkenazi Jews. By biblical law the knife may be made from anything not attached directly or indirectly to the ground and capable of being sharpened and polished to the necessary level of sharpness and smoothness required for shechita. The tradition nowadays is to use a very sharp metal knife. The knife must be at least slightly longer than the neck width but preferably at least twice as long as the animal's neck is wide, but not so long that the weight of the knife is deemed excessive. If the knife is too large, it is assumed to cause derasah, excessive pressing. Kosher knife makers sell knives of differing sizes depending on the animal. Shorter blades may technically be used depending on the number of strokes employed to slaughter the animal, but the normative practice today is that shorter blades are not used. The knife must not have a point. It is feared a point may slip into the wound during slaughter and cause haladah, covering, of the blade. The blade may also not be serrated, as serrations cause iqqur, tearing. The blade cannot have imperfections in it. All blades are assumed by Jewish law to be imperfect, so the knife must be checked before each session. In the past the knife was checked through a variety of means. Today the common practice is for the shochet to run their fingernail up and down both sides of the blade and on the cutting edge to determine if they can feel any imperfections. They then use a number of increasingly fine abrasive stones to sharpen and polish