mishnah berura 605.2 translation from feldheim
...There are/ localities where many /people/ gather together /for the slaughtering/ and they push one another. The slaughterers are awake all night with resentment and they do not feel the knife /to test it for notches/ owing to the considerable /amount of/ work /that they are required to do, so that the slaughtering/ can lead to /transgression of/ the prohibition against /eating/ neveylah. 1 In /these circumstances/ it is preferable to slaughter the kaparos a day or two before Yom Kippur, as the time /which is suitable/ for /the slaughtering of/ the kaparos is throughout the ten days of penitence. [P.Mg.; see there.] Alternatively, /people in these localities/ should circle money above their heads, which will be considered meritorious for them, so that they should not stumble into /transgressing/ the prohibition against /eating/ neveylah, Heaven forfend. [Someone who is able and wishes /to act/ in the choicest /manner/ should summon the slaughterer to his home in the early morning. Today it is the custom in several localities for the slaughterers to stay awake and go to everyone’s home after midnight until daylight. Therefore, it is proper for the slaughterers to sleep beforehand, so that they will not feel faint. In addition, they must prepare several /valid/ knives which have been examined. At the time when they slaughter they should see that they examine /the knife again/ each time and should not rely on the original examination. Now, even when the slaughtering is /done/ in the home of a householder it is usual for neighboring householders to come there as well. When one slaughters in his /own/ home, especially, many people who have been sent /to him/ with kaparos come together and due to the need to slaughter many kaparos there is insufficient time /for the slaughterer/ to apply himself sincerely to the examination of /the knife/ with the twelve examinations /required/ by the halachah. It is /therefore/ highly likely that due to the need to hurry /with the slaughtering/ he will not be meticulous over the examination. In view of this, the recommended solution is that, at any rate, after all the fowls of one householder have been slaughtered, /the slaughterer/ should examine /the knife/ before the person that /the householder/ sent with the fowls goes away /with them/, in order to ascertain whether his knife is satisfactory /for slaughtering/, as it is forbidden to eat /the fowls/ before this clarification /has been made/. If he discovers that /the knife/ is impaired, he should rule all that householder’s fowls to be tereyfah. 2 ]
1 I.e., the meat of a dead animal which was not slaughtered in conformance with halachic requirements. When the knife has a notch the slaughtering is invalid and the meat of the animal is therefore classed as neveylah.
2 In this context, what is meant is that they are not kosher. In more precise usage, the word implies that the animal or bird was slaughtered in conformance with halachic requirements, but it had a certain defect because of which it could not live, and in view of that it is not kosher.
ps in the bias hamikdash (and mishkan) it was (as today sometimes with corruption) and will soon be (acording to the opinions that we will have karbonois) (without corruption) very Commercial kosher slaughter