Thanks a bunch Unkle and Carl. 1. Yes, Unkle it appears that I have one key for everything. And I contributed to confusion by referring to a fuel cap rather than flap. The flap has a lock, not the cap. 2. Carl, the description you gave of a reversible key got me to do some more thinking (that hurt) and experimenting. Sure enough, pulled the door apart and serviced the lock, used the key upside down and presto! I can lock my door. Thanks again, much appreciated.