"This is our livelihood. We're a family business and there's been a lot of hard work over the years. We don't want to see that go down the gurgler," Mrs O'Brien said. "We're on a greater level of alert now than we've been before. We have to be."
The Wairarapa Times-Age yesterday reported 89 vehicles were stolen in the region last year, an increase on 2010. Of those cars, 26 were recovered.
Wairarapa police acting area commander Terry van Dillen said thieves were often either joyriders or "car ringers", thieves who steal cars for scrap metal and parts.
Mrs O'Brien said their company had a direct line to a specialised crime unit at the Masterton police station that speeds the reporting of suspect cars and metal.
"We have our own ways of picking out people we don't want to deal with and scrap that's suspicious," Mrs O'Brien said.
Their company was part of the Scrap Metal Recycling Association of New Zealand, which compiles an online "hot list" of stolen metals from which alerts are sent to members nationwide.
Fellow Masterton scrap metal dealer Nick McLachlan, who started Nick's Scrap Metals about three years ago, said he has likewise beefed up security at his Bentley St yard and is considering membership in the national scrap metal recycling association.
He said thieves had targeted the business before yard manager Vaughan Tocker started living on-site about two years ago.
He also runs a towing service that often recovers crashed and impounded vehicles for Masterton police, with whom the company has a close working relationship.
Mr Tocker said anybody offering metal for sale must provide photographic identification and all cars must pass a rigorous inspection to ensure ignition barrels and chassis numbers are intact.
He said a new metal compactor was set up at the yard about a month ago that demands a greater degree of vigilance "because with a compactor, you really can disappear a stolen car".
A security gate and fence have also been built at the yard to tighten security, Mr Tocker said.
"We do get offered all sorts, including stolen cars, but we want to keep things honest and you can tell if something's not right," Mr Tocker said.
"Dealing with criminals is the hardest thing you can do.
"They get pretty upset.
"But I'd prefer they just didn't come here with their stuff and, if we don't provide an outlet, then they just have to go somewhere else."