Though very few from the Edo period remain, the basic style remained unchanged until the World War II. One notable feature of the design is the 'sode-utatsu' wings extending forward on the sides of the upper floor. Their exact purpose is not certain, but one theory is that they were wind blockers, which is logical given Kanazawa's weather. Snow was also a significant factor in house design. The roofs sloped into a central garden that was designed to allow snow to collect as much as to provide light to the rear. While the sea of black-glazed tiles sparkling in the sun is a common tourist image of Kanazawa today, the traditional architectural style used wooden boards held down by stones. Due to the heavy snowfalls of the Japan Sea coast, traditional tiles were considered to be too heavy. The use of tiles on the frontage and boards under the eaves is to prevent snow damage.