Like many others here, major facepalm when first learning about the d-b menu. so much time manually quantum-stockpiling stones with loo(k).
Facepalm: Created an awesome dining room with artificial waterfall. it was a good design: river-fed cistern on the surface, catch cistern below the dining room, 4z pump stack powered by the river to reset it, floodgate to control filling the top cistern from the river and hatch to control release of the waterfall, everything hooked up to levers. I was even in a warm environment, so no worry about freezing
Well, on first activation, the thing didn't cause flooding, but it WAS making a wet mess, so I widened the hole in the floor and installed more grates, then turned it back on. Well, in that time a good deal of my initial upper-cistern full of water had evaporated from the barely-filled lower cistern. Easy solution! That's exactly why I left the fill lever available. I order it pulled twice to get a quick infusion of water.
The lever glitches out, and the floodgate stays open. Somehow or other quantum entanglement gets disentangled because I can never seem to order the floodgate closed. but that's okay, because the waterfall-controlling hatch is still in place.
The hatch was open when I ordered the refill, and the lever that controls it on the far side of the waterfall-fed dining room/meeting hall. Urist McNotASwimmer cancels pull the lever: Dangerous Terrain. As the river was basically at surface level, importantly above the mostly dug out level I was preparing to be a tree farm, cue Chapter III: Carp Fortress.