"I get it, Mike," said Joe. "I'll help." He added: "Chief! You watch Sanford. The rest of you try to flatten out some tin cans or find some with flat round ends!" He reached the spot where Mike bent over the plating. His hand moved to cast a shadow where the light had played. "I need more reflectors," Mike said brusquely, "but we can do it!" Joe beckoned. There were more, hurried clankings. Space-suited figures gathered about. The Platform rolled on through space. Where it was bright it was very, very bright, and where it was dark it was blackness. Off in emptiness the many-colored mass of Earth shone hugely, rolling past. Innumerable incurious stars looked on. The sun flamed malevolently. The moon floated abstractedly far away. Mike was bent above a small round airlock door. He had a distorted half-cylinder of sheet tin between his space-gloved hands. It reflected a line of intensified sunlight to the edge of the airlock seal. Haney ripped fiercely at other tin cans. Joe held another strip of polished metal. It focused crudely--very crudely--on top of Mike's line of reflected sunshine. Someone else held the end of a tin can to reflect more sunshine. Someone else had a larger disk of tin. They stood carefully still. It looked completely foolish. There were six men in frozen attitudes, trying to reflect sunshine down to a single blindingly-bright spot on an airlock door. They seemed breathlessly tense. They ignored the glories of the firmament. They were utterly absorbed in trying to make a spot of unbearable brightness glow more brightly still. Mike moved his hand to cast a shadow. The steel was a little more than red-hot for the space of an inch. It would not melt, of course. It could not. And they had no tools to bend or pierce the presumably softened metal. But Mike said fiercely: "Keep it hot!" He squirmed. His space suit was fabric, like the rest, but it had been cut down to permit him to use it. It was bulkier on him than the suits of the others. He shifted his shoulder pack. The brass valve-nipple by which the oxygen tank was filled.... He jammed a ragged fragment of tin in place. He pressed down fiercely. A blazing jet of fierce, scintillating, streaking sparks leaped up from the spot where the metal glowed brightly. A hollow in the metal plate appeared. The metal disintegrated in gushing flecks of light.... White-hot iron in pure oxygen happens to be inflammable. Iron is not incombustible at all. Powdered steel, ground fine enough, will burn if simply exposed to air. Really fine steel wool will make an excellent blaze if a match is touched to it. White-hot iron, with a jet of oxygen played upon it, explodes to steaming sparks. Technically, Mike had used the perfectly well-known trick of an oxygen lance to pierce the airlock door, let the air out of the lock, and so allow the outer door to be opened.