The garboard planks are the two closest to the keel, or in this case, on top of the keel. Since the boat is planked upside down, these are the first two planks to go on the boat. The planks, in case you forgot, are made of marine-grade plywood. A sheet of plywood is about 8 feet long and the boat is 14 feet long, that means that each plank comes in two pieces that need to get joined.