Dow produces Styrofoam building materials, including varieties of building insulation sheathing and pipe insulation. The upper gable walls are of milled lumber framing with shingle sheathing. The roof was made out of tongue and groove plywood, covered by copper sheathing. Housewrap is installed over the sheathing and behind the exterior siding. A plywood, stitch and glue (S&G) doesn't need fiberglass sheathing though some builders do. Metal step flashing is required behind overlapping seams to prevent sheathing damage from water. Some had hulls fitted with copper sheathing. An Open Crate is one that (typically) uses lumber for sheathing. The leaves are arranged in two rows with the petioles having a sheathing base. Her hull was fitted with copper sheathing, a process that took two weeks to complete. NM means "nonmetallic", referring to the outer sheathing; the conductors are of course still metallic. This wood sheathing had to be replaced. Several layers of protective sheathing, depending on the application, are added to form the cable. Seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers (integuments). Pillar 10 had the stays at the top strengthened with steel sheathing in the 1990s.