For trailers over 2000kg (Gross Trailer Mass) it is a requirement that a mechanism is in place in the event that if the trailer & tow vehicle separate accidentally, the trailer brakes are applied at full power for at least 15mins. One way to combat this is with a breakaway switch which sets the trailer brakes in case the trailer breaks away, however this is not to be used as a parking brake. It is nylon with a weldable tab.