Wal-Mart is rolling out shelf-scanning robots in more than 50 U.S. stores to replenish inventory faster and save employees time when products run out. The 2-foot (60 cm) robots come with a tower that is fitted with cameras that scan aisles to check stock and identify missing and misplaced items, incorrect prices and mislabelling. The robots pass that data to store employees, who then stock the shelves and fix errors. Out-of-stock items are a big problem for retailers since they miss out on sales every time a shopper cannot find a product on store shelves. Wal-Mart, the world’s largest retailer, has been testing shelf-scanning robots in a handful of stores in Arkansas, Pennsylvania and California. Walmart stresses that the robots are there to supplement humans, not replace them -- to eliminate drudgery and the expenses that go with it. This helps workers get to the task of filling empty shelves, and that is a job that the company does not see ending any time soon.