Section 2(l) in The Merchant Shipping (Tonnage Measurement Of Ships) Rules, 1960
(l)"Second deck" for the purpose of tonnage mark means the deck next below the uppermost complete deck which is continuous in a fore and aft direction at least between peak bulkheads, is continuous athwartships, and is fitted as an integral and permanent part of the ship's structure, with proper covers fitted to all main hatchways;
