By sunrise the seesaw already held two little cards, one for each board, resting where a child might later sit. The sand received a hello first. Only after the boards nodded to each other did the near end rise, no higher than a palm, as if height itself had been invited rather than taken.
The park keeper posted a note on the fence: guests may ride as usual; the invitations are only for the boards. There is no machinery to mention, only manners. A board that greets the sand does not startle anyone, and a board that is nodded to last never has to guess when it is its turn to be tall.
The day after, the same two boards returned with fresh invitations and practiced the palm-high lift once more, as if the first morning had been a rehearsal for being polite in public.