At The Mill Yard in Arcata, Calif., store manager Ed Cox keeps an eye on customers as they walk through the store. He's not just keeping track of what they're looking at; he's also noting where they stop and at what point they change direction. He then keeps this in mind as he sets the store and, in particular, decides what products to feature at his end caps. As a former manager at IKEA, the giant Swedish home furnishings chain, Cox knows that putting up barriers that require customers to stop in front of an item is a great way to increase that item's sales.