The Shechitah Process

Animal and Knife Positions

Standing (Omedet) or Lying Down (Munachat)

1. Shechitah for birds may be done by holding the bird down and cutting by moving the knife or temporarily fastening the knife upwards or downwards and passing the bird's neck along the blade. This may not be done for animals, though, for fear of Derasa by the weight of the animal. Moreover, in order to avoid future pitfalls, there is a rabbinic decree prohibiting any animal meat shechted in this manner despite the shochet's claim that he did not violate Derasa. Some argue that holding the knife steady from below and passing the animal neck along the knife from above has the same status. On top of that, some are further concerned that shechting from below when the animal is stationary is also problematic, unless the animal's head is tied upwards. If it's standing freely or lying down, that could be an issue even Bediavad. Therefore, some argue that ideally one should only shecht the animalwhen it is lying down with the neck below or to the side of the knife and stationary as the knife moves. Alternatively, the head can be tied and pulled upwards.
2. In this context, all birds are considered the same and all animals (Behemot Gasot and Dakot and Chayot) are considered the same. There is no distinction by species.
3. In modern kosher slaughterhouses, the Derasa concern in shechitah omedet is negated since the animal’s head is comfortably supported by a specially designed apparatus. Therefore, national hashgachot concur that this is an optimal form of shechita. Another device used in some slaughterhouses is an inversion pen, where the animal enters and is gradually rotated until it is lying upside down. It allows the shochet to cut with the more traditional downward motion. This machine was originally invented in 1927, called the “Weinberg Casting Pen”, with improvements made over the years. High costs and reduced efficiency preclude smaller operations from using it.

Machinery

1. A knife attached to a wheel and spun by human power (kocho) is kosher for shechitah regardless of whether one is actively spinning the wheel or spins it and lets go. Nevertheless, some express concern that perhaps it's rabbinically prohibited lest it lead to using knives set in motion by other forces other than the shochet's. It goes without saying that the shochet would have a harder time maneuvering such machinery and risks ruining the shechitah.
2. A knife attached to a waterwheel would be invalid for shechitah, unless one opens a dam of water that goes forth and spins the wheel. Still, only the first spin from the water would be valid, and some further argue that the first spin is lechatechilah invalid. Some also limit the circumstances to those in which the wheel is very close to the dam: if the water flowed for a considerable distance until it reached the wheel, that would no longer be considered the shochet's force.
3. There is no room for leniency if the wheel is attached to the ground.

Credibility & Dispute

1. If a dispute arises between the shochet and others regarding the kashrut of a shechita he did/they witnessed, there is much debate about the kashrut of the meat, depending on the circumstances, such as what the Shochet claims the issues were, if he made any excuses or made any marks on the animal, etc.