Where could a trap door, two thousand feet above the earth lead?
The operculum fits the entrance to its shell like a trap door.
This time, he woke with the slight creaking which the trap door made.
Then the trap door, relieved of his weight, flew back into place.
At one end of the buttery there was a trap door in the floor.
Throwing this aside, he unlocked the trap door and quietly raised it.
Then he shut down the trap door, securely fastened it and departed.
I guess the old duffer has it in his pocket, the same as he has the key to the trap door.
In the trap door was a small knot hole, about an inch and a half in diameter.
He might have gone down through that trap door while we was out.