Square Crank

Spike-ceiling trap: the free player goes back to the storeroom door that wouldn't open; the trapped player shoots its lock off from their side. Inside, pull the lever that stops the ceiling. The trapped player collects the crank in the spike room (in a safe, per Japanese guides).

Fits the gate socket under the main-hall stairs. One player turns it, the other goes through and turns the crank on the far side to let the first through. Carry on to the metal door and down to the underground prison.

Score Star #10 is on the ceiling of the lever corridor. Fandom calls it "Square Crank"; the exact in-game name is unconfirmed.