The first person inside the sacred precincts to greet the stranger is a keen-eyed "Petty Officer of the Guard." When the credentials have been examined the visitor is sent under the guidance of a bluejacket to the "Officer of the Day," whose "cabin" is inside the maze of corrugated iron and weather-board. The doors flanking the passages traversed display cryptic lettering, such as I.O. (Intelligence Office), S.R. (Signal Room), S.N.O. (Senior Naval Officer), "Commander" (usually the second in command of the base), P.M.S.O. (Port Minesweeping Officer), C.B.O. (Confidential Book Office), M.L.Com. (Motor Launch Commander), O.O.W. (Officer of the Watch), "Officers only" (the wardroom and gunroom combined), and, finally, the O.O.D., or the abode of that much-worried individual, the Officer of the Day, whose duties happily terminate when his twenty-four hours of administrative responsibility are over, only, however, to return in strict rotation. [Illustration: FIG. 17.--The central pier of a typical anti-submarine naval base. 1. Wardroom. 2. Sec. to senior naval officer. 3. Admiral's cabin (S.N.O.). 4. Flag commander (or lieutenant). 5. Base intelligence office. 6. Base commander. 7. Chaplain and gift store. 8. Drafting officer. 9. Store officer. 10. Chart-issuing office. 11. Cabin of the officer of the day. 12. Telephone exchange. 13. Warrant officers. 14. Pay office. 15. Fleet paymaster. 16. Paymasters and asst.-paymasters. 17. Writers and W.R.N.S. 18. Engineer-commander's office. 19. Men's quarters (for base duties and reserve). 20. Men's recreation room. 21. Petty officers. 22. Men's mess-room and adjoining galley. 23. Sick-bay. 24. Fleet surgeon. 25. Baths. 26. Baths. 27. Stores. 28. Boom defence office. 29. King's harbour master. 30. Hull defects office. 31. Police and cells. 32. Coaling office. 33. Wireless cabin. 34. Guard room. 35. Railway platform. 36. Sentry box. 37. Cranes. 38. Berths for armed yachts in harbour. 39. Motor launches in harbour. 40. Drifters. 41. Patrol trawlers. 42. Minesweepers. 43. Whalers. 44. Coastal motor boats. Larger ships, such as sloops, destroyers, "P" boats, coaling and ammunition hulks, lying out in basin.]