What did Lennie do on the ranch in Of Mice and Men?

From the text:

In a panic, Lennie looked at George for help. “He can do anything you tell him,” said George. “He’s a good skinner. He can rassel grain bags, drive a cultivator. He can do anything. Just give him a try.”

The boss turned on George. “Then why don’t you let him answer? What you trying to put over?”

George broke in loudly, “Oh! I ain’t saying he’s bright. He ain’t. But I say he’s a God damn good worker. He can put up a four hundred pound bale.”