The swap shop at the Northern Landfill in Westminster is open six days a week and is not restricted to Carroll County residents. It’s off Route 140, between Finksburg and Westminster, and is open Monday through Friday, from 7 to 4:30pm, and Saturday, from 7 to 3pm.
It’s a manned swap shop that accepts no upholstered furniture, nothing with Freon in it, and no tires.
I know someone who has been swapping there for years. Some of his finds include a full-sized Atari Arcade game, two pottery kilns, and some nice solid-wood furniture.