A grass-covered earthen embankment *doi 土居. The embankment is shaped like a truncated capital 'A'; it has a flat top, mabumi 馬踏, and widens towards the base. Shibadoi had a steeper slope than pounded earth embankments *tatakidoi 敲土居, and the outer slope of the wall, facing out of the castle, was generally steeper than the inner slope. The gradient varied depending on the school of architecture, but an incline *kōbai 勾配, of 3 in 1 was not uncommon for the outer slope of a grass-covered embankment.
The shibadoi was used in medieval and Edo period castles, particularly wherever a sharp incline was required, for example near the main entrance *koguchi 虎口, or at the base of towers *yagura 櫓, in encampments jinjo 陣所, and projecting compounds *dejiro 出城. Grass turf was piled on the lower section of a sloping, pounded earth foundation called tatakidodai 敲土台, and then secured with bamboo stakes and left to grow.