Cochrane however, with an immense quantity of sandbags, palisades, and barrels, made it pretty secure. But he did a cleverer thing even than this. There was a piece of steep rock, up which the besiegers would have to climb. This he covered with grease, so as to make it difficult to get a foothold, and planks with barbed hooks were placed ready to catch those who were rash enough to seek their aid.