Out of the upside-down plastic bag tumbled castoff items ranging from a purple-striped dog sweater to a pair of sequin-encrusted high-top sneakers. A handful of teens craned their necks to see what would emerge next.

For her contributions to the Lawrence Public Library’s Teen Swap Meet on Friday, 12-year-old Jamie McCoy received 12 tickets and promptly began glancing over other items for someone else’s stuff to spend them on.

The goal of the swap meet and other teen events is to get their age group into the library, said teen services librarian Karen Allen.

“I want to provide a community spot for teens to come to, where they can have a good time, engage each other and, hopefully, learn something,” Allen said, noting some teen events are more books-oriented and others are just for fun.

On Friday, Jamie’s dog sweater found a home with Chantel Guzman, 13, who thought it would perfectly fit her miniature schnauzer. Chantel also scored a ring and a bag full of buttons, including one picturing the band Paramore.

“I have an obsession for buttons,” she said. “I’m going to put them all on my school bag.”

Jacob Heath, 13, who visits the library a few times a week, said he was more excited about the swap meet before he showed up.

The only problem, he said, was that the girls — and their stuff — outnumbered him, roughly two to seven.

Nonetheless, Jacob picked up a few useful items. His favorite? A skull, from some kind of small animal. His most potentially profitable? A “Charlie’s Angels” DVD.

“I can sell it at Game Nut,” he said.