Lewis and Clark, racing Oregon's winter chill, built the 50 foot square Fort Clatsop, a double structure shelter with seven rooms, a sentry box, and a parade ground, in just 15 days. THE BIG BUILD's version is scaled down, but so is the timetable. Working in a dense patch of Kansas woodlands, John McPherson, a specialist in log structures, directs the team as they dig fire pits, raise raw wood walls, and fashion doors from rawhide. The end result may not be pretty, but it would keep the winter at bay.