In any case I would have the moral security of the rope, so I passed it through a fairly staunch pin close to the roof, which had an upward tilt that almost made a ring of it.

One end of the rope was round my body, the other was loose in my hand, and I paid it out as I moved.

Moral support is something.

Very gingerly I crawled like a fly along the wall, my fingers now clutching at a tiny knob, now clawing at a crack which did little more than hold my nails.
It was all hopeless insanity, and yet somehow I did it.

The rope and the nearness of the roof gave me confidence and balance.