After a hanging you could buy a piece of the hangman's rope. There were several reasons why people might part with their hard earned cash for such a macabre memento. One reason was that it was thought to bring luck to the buyer, particularly if the buyer was a keen card player. A second reason is that a piece of the noose was thought to prevent sore throats.
After a notorious villain, such as Dick Turpin had been hung, a piece of rope was bought as a comforting reminder that a bad fellow had met his just end - and perhaps a parent would point to the rope as a warning to a badly behaved child!
Such sales helped to boost the hangman's wages and a clever salesman would no doubt fuel superstition to boost his income.
Social history & Bygones