Two Salty Dogs in Boothbay Harbor has been collecting used tennis balls for a few years, and business has been good.

“It's totally maintenance free for us,” said employee Susan Reynolds. “People were bringing them in and dropping them off, or leaving them on the porch. We'd get big bags full — some were clean, some weren't. All we had to do was empty them into the barrel by the door, and people would come in and buy them.

“People get them and head to Barrett's Park with their dogs.”

You see the balls aren't for playing tennis. They go to the dogs.

When people donate their old tennis balls, Two Salty Dogs owner Don Kingsbury turns around and sells them to dog owners with fetch-crazed dogs. The proceeds go to The Lincoln County Animal Shelter. “Last year we gave the Shelter hundreds and hundreds of dollars from the sale of your used tennis balls,” Kingsbury said.

Employee Susan Reynolds said she thought they had a never-ending supply. Until recently. “We had a bazillion of them, and we thought we'd never run out, and now they're almost gone.

The balls sell for three for a dollar. “It's a cheap toy,” Reynolds said. “You can lose them, the dogs can bury them, and it's no great loss.”

So don’t throw your old tennis balls away. Drop them off at Two Salty Dogs during business hours or just leave them out back by the back door.