There's one key. But there are ten numbers. JUST SAYIN'
Everybody has different things in their lives. Some things they don't care about. Some things they care about a great deal. Some things they pretend not to care about while actually caring about. And some things they hope that nobody, but nobody, ever actually discovers. For the former, a simple lock will do. For the latter? You need AS MANY LOCKS AS POSSIBLE.
So if you don't want your friends finding out you write fanfic about the cast of 1776, maybe consider buying a Kwikset SmartCode Electronic Keypad Lock for all the doors between your guests and your writing room. Without the special code, the handle simply won't turn, and then no nosey so-and-so is gonna get their peepers on the unfinished chapter where Jefferson first seduces John Adams in the hot tub underneath the Liberty Bell.
See? SEE? Your face right there is why people like ME have to keep my work under lock and key. Why can't you just LET THE GENIUSES CREATE????????