Lath and plaster - Wikipedia
The wall or ceiling finishing process begins with wood laths. These are narrow strips of wood, or split boards, nailed horizontally across the wall studs or ceiling joists. Each wall frame is covered in lath, tacked at the studs. The lath is typically about one inch (2.5 cm) wide by four feet (1.22 meters) long by 1⁄4 inch (6.4 mm)