The turned brass pillar support, at the stern. A 4.5mm drill shank goes through this (and the one at the bow) into a brass tube set into the hull. For the centre pillar, an M5 machine screw is threaded into a steel block fixed out of sight between frames 23 & 24. Also visible is the "steam band" running around the keel, and the keel strap which strengthens the joint between the keel and the sternpost.