The key to any fix is to reunite the plaster with the strips of wood lath underneath. Otherwise the cracks come back, no matter how many times you patch over them. That's why This Old House general contractor Tom Silva usually reattaches lath with screws and metal washers before attempting a repair. Recently, though, he tried Big Wally's Plaster Magic, a homeowner-friendly adhesive that uses glue instead of screws. While it costs more than the screw-and-washer method—a six-tube kit runs $120, versus $20 for 120 metal washers—the final finishing is easier and looks better because there aren't any washers to cover. Plus, a glued bond lasts longer than a screwed connection.