CHICAGO — Sears Holding Corp. said Wednesday that more than 7,000 job openings at Sears and Kmart will be posted on Twitter, a move experts say is a way to advertise and market its brands to 18- to 34-year-olds, the mainstay of the social networking site.

Sears Holdings said the tweets will be posted by TweetMyJobs .com, which handles similar postings from McDonald’s and Motorola. Though Twitter is free, TweetMyJobs.com charges from $4,000 for 500 postings to $8,000 for unlimited postings, said Rich Trombetta, a company co-founder. It charges $1.99 for single posts.