Or Grantaire, in theory -- he does know it, even if he was never one for producing or caching seditious materials -- but Enjolras has no idea whether he's ever bothered to employ it. Certainly Grantaire knocking at the door of his lodgings is snot omething he's personally experienced, whether or not it's the tell-tale pattern that states I'm of the inner circle of the Amis de l'ABC, and no one who isn't is with me.

Unlocked. He enters.

(A gift, still, to be able to do this. A gift to knock on a door and hear a beloved voice, enter and find a friend smiling.)