A lot of interior designers are getting tacky—as in, using furniture tacks in upholstery. Anyone who follows interior design has seen the increasing use of furniture tacks outlining the edges of chairs, headboards and ottomans. The finished look is called nailhead trim, and it's become so popular you can find upholstery tacks in every finish under the design rainbow. Want to give your furniture more definition? Just put a nail in it.