For 15 years or thereabouts, the Walker Art Center’s frame shop has held a one-day sale, open only to staffers, to clean house of the dozens of hand-built frames from exhibitions past that are no longer usable. The latest was Wednesday — and my first here on staff — and I was stunned to see loads of sturdy, elegant wood frames of varied sizes for less than $10. Bargain-conscious staffers streamed into the Cinema, cash in hand, when the doors to the Walker Cinema opened at 10 am (My rookie move: Leaving my wallet at my desk). The smallest frames, which are the most functional and practical on living room walls, were the first to go. Some staffers horded a dozen or more, squirreling them into a corner to measure them, before committing to the all-sales-are-final buy.