A knacker (/ˈnækər/), knackerman or knacker man is a person who removes and clears animal carcasses (dead, dying, injured) from private farms or public highways and renders the collected carcasses into by-products such as fats, tallow (yellow grease), glue, gelatin, bone meal, bone char, sal ammoniac, soap, bleach and animal feed. A knacker's yard or a knackery is different from a slaughterhouse or abattoir, where animals are slaughtered for human consumption. Since the Middle Ages, the occupation of "knacker man" was frequently considered a disreputable occupation. Knackers were often also commissioned by the courts as public executioners.