One would think the Gate Cutters Jewelry Crew, a criminal gang that has robbed 50 jewelry stores since 2003, has a bad business model. Their modus operandi is to cut a jeweler’s gate, snatch all the jewelry that’s not in the safe, and flee after a few minutes, before anyone responds to the tripped alarm.

But most jewelers don’t leave expensive jewelry outside their safes after hours, right? And how much can a gang grab in three minutes?

It turns out, plenty. Among the Gate Cutters’ hauls: $330,000 worth of jewelry from a store in Boca Raton, Fla.; $260,000 from a store in Maryland; and $213,000 from a store in Pennsylvania. All told, the gang is estimated to have stolen $5.1 million worth of jewelry.

All of which demonstrates that many jewelers aren’t following basic burglary-prevention procedures. Security experts say jewelers should not leave any jewelry lying around at night, never mind several hundred thousand dollars’ worth.

“The sad thing is most burglaries are preventable,” says John Kennedy of Jewelers’ Security Alliance. “Too many jewelers are leaving their merchandise out and ignoring the recommended steps.”

The bad guys are noticing: While jewelry crime has generally dropped, burglaries are hitting record levels. In 2005, there were 370 burglaries, up from 290 in 2004, JSA says. An estimated 70 percent of those were so-called three-minute burglaries, rush jobs where criminals snatch whatever’s not in a safe.

To prevent your store from being added to the list, experts offer the following advice:

Put away all jewelry at the end of the night. Experts say that leaving jewelry in a showcase—or worse, on a repair bench—is akin to leaving dollar bills piled on your counter. Even less-expensive goods should be tucked away, Kennedy says: “We’re not saying lock every piece of low-end merchandise in a high-end safe. We’re saying lock it up somewhere. It can be in a metal drawer, it can be in a cheap safe, but somewhere where it will take time and make noise for burglars to get at it.”

Kennedy knows the reasons people leave their merchandise out: They don’t have time to put it away, there’s no room in their safe, or they don’t want to scratch the pieces. Still, these problems pale in comparison to the costs of a loss. Even minor burglaries can mean spending hours dealing with the insurance company and police, damage to the store, increased premiums, and decreased employee morale.

Don’t cover your cases—even if they’re full of merchandise. “If you put cloth on a case, criminals assume there is something in there,” says Dave Sexton, vice president of loss prevention for Jewelers Mutual, Neenah, Wis. And if nothing’s in there, it doesn’t make any sense to cover them.

Use burglar-resistant glazing, proper deadbolt locks, and 24-hour surveillance cameras. Make sure the glass is installed properly, Sexton says. “Getting the right material is great, but it has to be installed by a qualified professional according to the manufacturers’ instructions. If the glass is not installed properly or in a weak frame, it can just be popped out.”

Regarding cameras, “Make sure they’re maintained and working properly,” Sexton says. “A lot of jewelers put in the cameras, but then a year later when they need them they don’t work.”

Keep your stores well lit at night. “You want to keep the general area lit so police or anyone else passing by can see what’s going on,” Sexton says.

Install your security gates on the inside of your glass. “Then once the alarm is set off, the gang has to also cut the gate,” Robert W. Frank, JSA vice president and former policeman, says. “And usually that takes too much time for them.”

Consider having a “security survey.” A consultant examines your store for security vulnerabilities. Some insurance companies provide it.

These steps can cost a considerable amount of time and money, but burglaries are becoming too prevalent for jewelers to ignore. As Kennedy puts it, “This is the kind of thing that allows you to sleep at night.”