The cages can also be used for inspections and even rescues, and all stevedores use them as part of their daily work.
Mr Haretuku, 52, and Mr Tahiwi (who says he's "middle-aged") have worked for Ports of Auckland for more than 20 years. Their job is to train stevedores - from crane and straddle drivers to lashers and leading hands - to carry out their roles in a safe and professional manner.
Mr Haretuku started as a store man with the then Auckland Harbour Board back in 1987.
"I was originally attracted to the Port because of the different types of machinery that operate there," he said. "I have progressed from where I started to my current position."
Mr Tahiwi, whose official job title, like Mr Haretuku's, is "operational performance coach", has been in the job for two years, but has worked at the port for 20.
His involvement with Ports of Auckland began back in the 1980s, but he officially joined its staff in 1994.
"I've had the opportunity to train on numerous types of heavy and light machinery, leading hand positions and for eight years was part of the planning and capacity team," he said.
Those wanting to get a ride in a personnel cage on Saturday will see what it takes to be a good crane driver.
Booking is essential, and 10 people can fit in a cage. Call 0800 AK PORT (0800 25 7678) for more details.
Free boat and bus tours of the port are also available on Saturday, Sunday and Monday. Visitors can also try out a ship simulator at the Maritime School of New Zealand.