And then about twelve feet from the ground I struck the first of the iron pegs.
To this day I cannot think what these pegs were for.

They were old square-headed things which had seen the wear of centuries.

They cannot have been meant to assist a climber, for the dwellers of the cave had clearly never contemplated this means of egress.

Perhaps they had been used for some kind of ceremonial curtain in a dim past.

They were rusty and frail, and one of them came away in my hand, but for all that they marvellously assisted my ascent.
I had been climbing slowly, doggedly and carefully, my mind wholly occupied with the task; and almost before I knew I found my head close under the roof of the cave.