Extricating a stuck lorry with the help of steel channels. Craig on left, Prendergast facing, Bagnold on right.

"... in addition at the last moment Prendergast thew on board the two old steel channels that we had collected three years before for crossing ditches in Sinai. ... Every few miles one or other of the two lorries would get stuck in the soft ground, the back wheels sinking in and merely spinning round, digging themselves ever deeper as long as they were forced to turn. If it had not been for those old steel channels we must have given up after the first three days and gone back to Cairo. They were the salvation of the expedition. They provided an unfailing way of extricating a car or lorry which no amount of pushing could move."

(R.A. Bagnold, Lybian Sands, London, 1935)