The windows have stone surrounds, mullions and transoms. Mullions are vertical elements and are often confused with transoms, which lie horizontally. It has plumb stems, reverse transoms, transom-hung rudders controlled by a tiller and no keel. Horizontal transoms sometimes had to be introduced to strengthen the vertical mullions. The windows are polished plate glass with stained glass transoms. There are ventilation transoms above some interior doors. These motifs recur in the stained glass window transoms. Outboard motor shaft lengths are standardized to fit 15-inch, 20-inch and 25-inch transoms. The decking is of timber, supported on trussed wrought-iron transoms. These were analogous to the prism transoms used over above-ground windows and doors. Doors and transoms were burned through on all but the fourteenth and fifteenth floors. Two of the stores still have the original ornate transoms. These are often further braced by horizontal transoms. Thinner timber transoms were used to keep the baulks the correct distance apart. Twin backstays run to the transoms, enabling the forestay to be kept taut.