I haven't done a chitty set in a while. This is a tool for building a dungeon on the fly. I made it to help get myself through a dungeon I'm making up as we play. Instructions:
Cut out the chits.
Place the Entrance chit.
As the PCs explore, you furtively draw (or choose) chits to place next to the entrance chit to make your DM's map. Most of the chits are functional rather than descriptive, like "Neutral Power" and "Impassable." If you draw the "Dormant Threat" chit, for example, you can decide whether it's a crypt of animated skeletons, a sleeping dragon, or a gargoyle dozing in a niche on the wall.
Some chits may need some explaining. "Key 1" corresponds to "Lock 1" and "Key 2" corresponds "Lock 2." They don't literally have to be keys and locks but you need something at Key 1 that gives PCs access to Lock 1 and something from Key 2 to access Lock 2. It could be a magic phrase, a clue, a scroll, whatever, as long as it's functionally a key and lock problem.
As you build your DM's map, you can describe the rooms however you like, and mark connecting passages and doors between the rooms that link the chits together.