It soon became obvious that more longitudinal strength could be achieved by running the frames longitudinally (fore and aft), provided that reasonable transverse strength was maintained. With the coming of steamships, racking stresses became less important, but hogging and sagging stresses became more serious as ships grew longer. This was partly because it was cheap to build and served its purpose and partly because a suitable alternative was not available for many years. This system is not the most efficient for steel steamships, but it has continued in general use until recently. Longitudinal strength was less important in these ships because they were comparatively small and hogging and sagging stresses were not large. This stress tended to distort the transverse shape of the ship. The sailing ships with their masts and sails exerted a considerable stress on the hull. It was also necessary to use transverse framing because sailing ships needed considerable transverse strength to enable them to resist the stresses set up by the masts and rigging. Wooden ships were always built on this system, because closely spaced transverse frames were needed to hold the planks together so that seams could be caulked. Where openings in decks are required, they are discontinued and strengthened at these openings to compensate for the loss of strength. Transverse frames run from port to starboard. Frames when connected to the transverse be make up the ribs of the ships.