Gary Correa is a 20-year veteran of a little-known group of Honolulu residents that, for enjoyment and a little extra cash, regularly bids on the contents of delinquent self-storage lockers.

He has unearthed gold jewelry and antique Hawaiian sheet music, and was hoping for another big find last month inside a locker full of concrete chunks, rusty pipes and mysterious boxes taped shut.

"I'm taking a gamble that there's something good in those boxes," Correa said as the auction for Hawai'i Self Storage Locker No. 1063 ended with his winning bid of $80.

But Correa's hopes were dashed as soon as he opened the boxes. Every one was filled with rocks.

"That's how it is," said Correa, a 53-year-old security guard from Waimanalo, as he loaded the concrete blocks and 20 or so rock-filled boxes into the back of his van to take them to the dump.

An abundance of stuff and a shrinking amount of living space has spurred the growth of public storage facilities in Hawai'i in the last five years. It's also created a small but growing number of people such as Correa who seek out public storage auctions, looking for abandoned items to collect or sell.

"Jewelry, money, coin collections, antiques — you can find just about anything in these lockers," said Steven Ortiz, 71, of Foster Village, who has been attending storage auctions for about 35 years.

With 40 self-storage facilities on O'ahu and 17 more in the works, Hawai'i will soon have the equivalent of 3.9 square feet of self-storage space per resident. When renters stop paying, the facility can sell locker contents to reclaim some of the losses.

There are about five or six auctions per month on O'ahu, according to those who frequent auctions. Legal notices for auctions appear in The Advertiser three or four times a month.

Managers at Hawai'i storage facilities say they have seen expensive jewelry, antique furniture, big-screen TVs and personal watercraft tucked away in the backs of lockers. In Dallas, Pat Stokes, now a property manager at Ala Moana Self Storage, even spied a piano and an abandoned car on the auction block.

"It's a great treasure hunt," said Nancy Durrett, 40, of Mililani, who started bidding on lockers six months ago. "Sometimes you find something, sometimes you don't. But stories like that keep you coming back."

Storage facilities encourage bidders to return any personal items, such as photo albums, birth certificates or — in some cases — the ashes of loved ones.

The Service Members Civil Relief Act prohibits the sale of military people's belongings if they are deployed overseas. An estimated 6 percent of the 1,400 units in Hawai'i Self Storage's Pearl City location are rented by military personnel on deployment. Nationwide, about 4 percent of units are rented by military personnel, according to the National Storage Association.

Tales abound from the 1980s and '90s when self-storage facilities were fewer and bidding on abandoned lockers was still an unknown art. There was the locker full of priceless maps, wooden bowls and gifts from foreign dignitaries to Hawai'i. There was one containing Hollywood film reels and one with the ostrich skin boots of a famous drummer.

But auction-goers say the finds aren't what they used to be.

People who could afford a locker 20 years ago would also store items of greater value, said Shaun Salvador, manager for Hawai'i Self Storage. Now people from all walks of life use self-storage, from displaced families to college students studying abroad for the summer, so auctions are more of a gamble.

The Self Storage Association estimates that nearly one in 10 American households currently rents a self-storage unit, an increase of 65 percent from 10 years ago. With more than 78 square miles of rentable storage space in the United States, Americans now have an area more than three times the size of Manhattan in which to store their things.

On auction day, most storage places cut the lock on each locker in front of bidders, who are only allowed to inspect the contents while standing outside the locker. For that reason, a strong flashlight is a must. Bidders also come with trucks to haul the stuff away and padlocks to put on the lockers they've bought.

POT OF GOLD — OR ROCKS

At a recent Hawai'i Self Storage auction, manager Joe Beierly started the bidding at $20 for most lockers. Bidders were most interested in a locker packed wall-to-wall with items concealed beneath cardboard and brown wrapping paper. The care with which the owner had wrapped the contents stirred their interest, and the unit went for $950.

A larger unit with an expensive-looking couch and matching pillows, plastic plants and decorative marble columns sold to Stephany Aplaca of Wahiawa for a mere $90.

Back in the parking lot, Correa loaded the last box of rocks into his van and ignored the exasperated looks his daughter was shooting his way.

"Everybody that buys a locker is hoping there's a pot of gold in there," he said, grinning. "Then we go home and kick ourselves."