Safety chain connections (shackles, pins or bolts)A suitable shackle is where:
the shackle is rated and complies with Australian Standard AS 2741-2002 “Shackles”
or other equivalent recognised standard; and
the break load limit of the shackle is rated at least 1.5 times greater than the ATM of
the trailer.
Took this from Qld Transports Safe Towing Guide