1What is on it
Two basins with foot-operated pumps so nothing is touched by hand, soap dispensers, a paper-towel holder and a waste bin. Fresh water is carried in a tank underneath and used water drains to a separate sealed tank, so no plumbing or hose is involved.
2Where it belongs
To the side of the units, at the end of the bank, with room for two people to stand and reach the pumps without blocking the doors. At a food event it goes near the vendor line as well, because handlers need one within easy reach of where they work.
3Who has to have one
Food-service events are the usual case — health inspectors expect hand-wash provision for anyone handling food. Job sites with a lunch trailer, sites doing dusty or dirty work, and anything running long enough that people eat on site all benefit whether or not it is required.