How does Polyphemus attempt to keep Odysseus and his men from getting out of the cave?

"But the Cyclops there, still groaning, racked with agony , groped around for the huge slab, and heaving it from the doorway, down he sat in the caves mouth, his arms spread wide, hoping to catch a comrade stealing out with sheep-- such a blithering fool he took me for."

Robert Fagle's: The Odyssey

page 224 between section 460 and 470