[lowfighter]

Maybe this description can help too (from Frazer's book about Rommel):
"The defences of Tobruk, prepared by the Italians, consisted of two concentric perimeters, separated by some two thousand yards from each other. In each perimeter were a number of defensive nests, concealed dugouts and fire positions connected by communication trenches, eight feet deep,and with emplacements designed for mortars, machineguns and anti-tank guns... Each of the defensive position was planned for about forty men and was roughly circular with a diameter of some ninety yards. There was of course extensive wiring. Tobruk was formidable."


Edit: and here I found a sketch of a strongpoint at Tobruk: