It is not clear when translucent shoji were first used. The symmetrical round-pillared shinden style developed in the mid-900s, for the lakeside palaces of aristocrats. The outside could be closed off with heavy wooden shutters called shitomi-do (), which were usually horizontally split and hinged (hajitomi), but were occasionally vertically split and hinged. Sliding partitions (hiki-do, , literally "sliding door") did not come into use until the tail end of the Heian, and the beginning of the Kamakura period. Early sliding doors were heavy; some were made of solid wood. Initially used in expensive mansions, they eventually came to be used in more ordinary houses as well. Smooth fitting of panel and groove is critical to allow the panels to move easily, and the woodworking of the sliding mechanism developed over time (modern shoji can be moved with one finger). Formerly, the grooves were made by dobumizo (), nailing strips of wood to the kamoi (lintel) and shikii (sill) beams. The grooves were later cut into the beams, using a specialized saw to cut the sides, a chisel to remove the waste, and specialized groove planes to smooth. A shakuri kanna (plow plane) was used to smooth the bottom of the groove, and a wakitori kanna for the sides of the groove (these planes also became more elaborate, later adding screw adjustments and other machined-metal refinements). Before hiki-chigai (sliding panels that overlap when closed) became standard in the Muromachi period, hiki-do had a central vertical rail (nakahōdate, ) in the middle of each opening to cover the gap between the panels when they were closed. In the Muromachi period, hiki-do improved, and the Shoin style of architecture was developed. The rising warrior class seeking to emulate the aristocratic fashions, and the aristocrats, who had lost wealth, could no longer afford Shiden-style palaces. Conrad Totman argues that deforestation was a factor in the style changes, including the change from panelled wooden sliding doors to the lightweight covered-frame shoji and fusuma. A core part of the style was the shoin ("library" or "study"), a room with a desk built into an alcove containing a shoji window, in a monastic style; this desk alcove developed in the Kamakura period. The Shoin style also made extensive use of sliding doors. In order to fit better against closed hiki-do, support pillars were squared; these were called kaku-bashira (). Suspended ceilings were added, and tatami were