Japanese architecture has traditionally been typified by wooden structures, elevated slightly off the ground, with tiled or thatched roofs. Sliding doors (fusuma) were used in place of walls, allowing the internal configuration of a space to be customized for different occasions. People usually sat on cushions or otherwise on the floor, traditionally; chairs and high tables were not widely used until the 20th century. Since the 19th century, however, Japan has incorporated much of Western, modern, and post-modern architecture into construction and design, and is today a leader in cutting-edge architectural design and technology.