Every home can use another shelf unit especially when you build it. Fill it with prized collectibles, photos and artwork, display pieces, or even books. This sturdy, yet highly stylish, design from the Meier brothers, Christian and Robert of Santa Cruz, California, fits nearly anywhere. As an added bonus, you'll learn the ins and outs of the loose tenon, a joinery method that involves making mortises in two mating parts, then joining them with a third piece, the loose tenon. The name refers…