Monday's Riddle! A Secret Way In...

Hello Riddlers! Can you guess the theme? The DMS is all about this. ; ) ~ F

A sequence or pattern put into place, left to leave an unmarked trace. Those who figure out the key, will surly unlock a mystery. Open Sesame gets you in. With the right numbers you're bound to win. A password or secret known by you, leaked to another if that's what you do. It could be a name or date of birth. It can hide something small or of measurable girth. A puzzle or word that opens a door if, of course, you're the person it's for. 

What am I referring to? 

I gave you a clue! 



FEAR NOT THE UNEXPECTED