Toki no fuda (a board for time) (時の簡)
The Toki no fuda was a board that was placed in a small garden in the Seiryoden (literally "Limpid Cool Hall") to show time.
The Toki no fuda was supported by a stake and replaced over time, and naiju (government official especially one of low to medium rank as royal pages) took charge of the replacement.
"Kineki hisho" (禁腋秘抄) (a text describing rules and etiquette to be observed in the Seiryoden and Shishinden [The Throne Hall]) described the location of Toki no fuda, that 'c. 3.6 m from a station that is staffed with retainers, and tsumado (a side entrance, hinged plank door that was placed at the four corners of the enclosure of a aristocrat's mansion) on the east side and the next c. 1.818 m is shitomi (a wooden lattice door which opens up vertically).
Open shitone, put down the west side door and stand the pantry shelf in front and place Toki no fuda bear by.'
It supposed to be dividing the day and night of 12 hours into 4, then inserting the stake of time only on the 4th time.