Keen 4 Plaks

[troublesomekeen]

Good afternoon! By way of celebrating my latest successful Tile Property extravaganza, I was doing a bit of Galactic translating. I've been playing Keen all my life, but I never took the time to investigate those yellow plaks embedded in the walls with strange red letters. Finally got around to it. One of them says "Exit" (also the wooden and metal signs) and another says "Watch out." I know all you guys and dolls knew that already. But it's new news to me.
Now, if I translated this properly, one sign says "High Low." What exactly is that supposed to mean?

[Ceilick]

It's indicative of a switch that affects a vertical goplat.