Reached through UPDATES. The sparkle over a chamber's socket, built with it (object templates 24 to 27, flags $12: out of the collision tests). It hovers 13 above the socket and steps through four frames (graphics 108-111 share the sprites of the sparkle a thing dies in), and when the frame comes round to the socket's kind it shows the valve wanted (WANTED_VALVE) for two turns: about two turns in six. Like the picture, it goes when anything lies in the room from the places.