Or, suna setchin, 砂雪隠 (snow-hide).
A feature of some Japanese tea gardens, located near the inner waiting bower, symbolic of a host's regard for his guests…no, that’s not quite the right idea…
In order to explain this rightly, you have to remember that every detail of a tea garden serves some purpose. There is a distinction between the inner and outer gardens (and perhaps one or more additional zones), in that worldly cares are, perhaps, still present, in this outer zone, and can be purified in this liminal space. Here one might find a working lavatory, whether modern (with adaptations) or traditional, meant to be used to refresh the guests, a place to change into traditional garb, etc.
The operative word for this part of the garden is “pretty”. There might be flowering plants, eye-catching decorative elements, things that charm and interest. It looks like a garden. Things are planned, and what is part of the human realm (like that improbably steep-looking bridge) is clearly defined. It's "worldly", in short.
Passing through the gate (or several) to the inner garden however, you move into a world where the line between natural and cultivated becomes confused. There are no flowers here, but for perhaps one spring-flowering tree, and only a few reminders that this place is a garden at all – you might as well be walking in a secluded bit of forest, perhaps the grounds of a shrine, except that...it's got all the rotten trees and thorn bushes cleared away, and everything is just so green...even in seasons and times where it ordinarily wouldn't
be. There's a place to wash out your mouth with a dipper of water, and maybe a lantern (that looks great when there's snow on it)...and the path in autumn, has just the right amount of maple leaves on it. Maybe you'll catch sight of a pile of leaves, like sweepings, but they look...too perfect. It's so..round, and the leaves and twigs look so much like a pattern. Is that a real dry streambed, or some rocks and earth arranged to look like one? It's hard to tell what "just happened that way" or what someone spent a lot of money, effort, and time to make it look..so natural...
You see the teahouse. It's a tiny hermit's hut, maybe ten feet square, with a kitchen in back...but it looks better than a real indigent's shack ever did -- more like an architect's idea of a hermit's hut. It's there that you'll wait in a little shelter, perhaps with tobacco and a one-hit pipe for amusement, and not far from this, half-hidden behind a bush, you'll see a six-foot square, deep patch of sand with four stones around a hole, a pitcher of water and a paddle, stuck in a small sandpile off to one side. If you didn't know what it was, you'd think it was just a sand-and-rock sculpture.
This is the suna setchin, known as the Hidden Sand, or Hidden Snow. (What, you were expecting, a little house with a moon carved in the door?) You stand on two of the stones, and do your business, cat-wise, in the hole. Then you use the pitcher to wash yourself off, the paddle to throw some sand in to keep out flies, and you're done. Only, this is never to be used.
In a monastery, every day, the Abbot himself, or some ranking senior monk, digs out the hole and puts the contents in a container to be taken away as fertilizer in a nearby farm, and lays down more sand. Surprisingly, this is considered the "plum" job in the monastery, and a great honor, although it might be considered, outside of monastic life, to be the province of the lowest of the low. (Latrine detail is the traditional first job of every girl training to be a geisha. Think about this for awhile.) This is part of the paradoxical nature of life in a monastery: relatively easy, untaxing jobs like paperwork are of low status, and considered strictly novice material, while those that call for manual labor and unpleasantness are much sought-after as a chance to put all that mindful detachment to good use. This helps to keep things egalitarian -- since everyone wants to get respect from their peers, even the worst jobs get done to perfection.
Also, in the era when tea culture was developed, nearly every samurai had spent some time in a monastery, much like how the British Victorian middle class had been to boarding school. So, perhaps not in the tea room itself, but in the waiting shelter, they might smoke and joke with each other about how the sight of the privy brought back memories, and so on. (I guess men will be men, all over.)
So important a detail this is to a tea garden that among the artifacts traditionally attributed to Sen no Rikyu, the founder of the modern tea ceremony are his favorite tea bowl, his tea scoop, and...his personal paddle.