In the Zen temples of Rinzai school, the Sodo is the particular hall where a group of trainee monks strictly train themselves through their rigorous practices such as Zazen (sitting meditation).
Along the inner walls of this hall, the small discrete spaces called "Tan (unit)" are arranged in a row. This "Tan" is one Tatami mat (about 180 by 90 cm) in size and is provided as the individual practice space where each trainee monk lives in poverty and sits in meditation every day.
The entrance of Sodo is always left open even in winter. On the wooden board hanged beside the entrance, the characters of "Zazen" is inscribed.