It’s a fool’s way to sell gold.

Hocking bling for big bucks to sandwich-board-wearing buyers sounds like a quick way to profit, but during a sweeping, six-week sting, the city Department of Consumer Affairs found that 74 percent of 450 gold buyers violated the law.

Many also used sneaky — but legal — tactics to lowball clients.

That’s something the agency hopes to change.

There’s been a rush to unload gold pieces since the metals market skyrocketed.

“No matter where I went, it was the same: real lowball offers and the same treatment. I felt pressured,” a DCA undercover investigator told The Post.

The agency issued $500 tickets to more than 300 shops for violations such as false advertising, not posting required signs and not keeping proper sales records.

Other shady practices — such as fraudulent scales, commingling varying karats, downgrading karats and failing to post the daily market value of gold — are not yet illegal.

DCA Commissioner Jonathan Mintz is proposing a set of transparency regulations, including a measure to create a highly detailed receipt to record the exchanges so the agency could better help consumers.