Openings. Unless the tops or openings in a brick wall are well arched, or have a stone, metal, or wood lintel showing in the face of the wall, they should have a beam of steel, or of thoroughly seasoned wood, to support the wall above, resting at least 4 inches upon the wall at each side of the opening, and visible only from the back or inside of the wall. A double rowlock, or relieving arch, should be laid above the beam or lintel, showing upon the inside of the wall, as illustrated in Fig. 16 at a, or b. An anchor should be placed to. resist the thrust of the rowlock arch as shown at c.