, circa 1967 In the twenty-first century, the
kotatsu typically consists of the electric heater attached to the frame, which is no longer limited to wood, but may be made of plastic or other materials. Generally, a blanket (or
shitagake) is draped over the frame and heater and under the table-top. This first blanket is covered by a second heavier blanket, known as a (). A person sits on the floor or on
zabuton cushions with their legs under the table and the blanket draped over the lower body. The
kotatsu was designed when people most commonly wore
traditional Japanese style clothes, where the heat would enter through the bottom of the robes and rise to exit around the neck, thus heating the entire body. Most Japanese housing is not insulated to the same degree as a Western domicile and does not have
central heating, thus relying primarily on space heating. Heating is expensive because of the lack of
insulation and the draftiness of housing. A
kotatsu is a relatively inexpensive way to stay warm in the winter, as the futons trap the warm air. In the summer, the blanket may be removed, and the
kotatsu used as a normal table. It is possible to sleep under a
kotatsu, although unless one is quite short, one's body will not be completely covered. This generally is considered acceptable for naps, but not for overnight sleeping for many reasons: one's body is not completely covered, yielding uneven heating; the table is low, so one may touch heating elements accidentally when moving while asleep, risking burns. Traditionally, children are told that they will catch a cold if they sleep under a
kotatsu. Pets, such as cats, frequently sleep under
kotatsu, however, and are small enough to fit completely underneath—comparable to cats who sleep on floor heating vents in Western countries (Japanese homes do not generally have floor heating vents). During the winter months in Japan, the
kotatsu often is the center of domestic life. In the evening family members gather around the
kotatsu to enjoy food, television, games, and conversation while keeping the lower half of their bodies warm. It has been said that "once under the
kotatsu, all of your worries slip away as a familiar warmth takes over and you become completely relaxed." Historically, were made of
bast fibers. Later, cotton was introduced (1300s to 1700s, depending on region) and they were usually made of bast-filled quilts of recycled cotton, dyed with indigo and pieced from old garments in
boroboro style. , for going under the , as a floor covering, were made the same way. In the 2010s,
kotatsu-gake were often decorative and might be designed to match home décor. ==Other countries==