Lockpicking

A professional lockpick isn't afraid of any lock. Mainly because locks don't actually pose a threat, being inanimate, inert objects meant only to secure objects. Also because a professional locksmith can open up these locks pretty quickly. Hell, they pretty much only have to touch these locks, as no mention of needing lockpicks has ever been made.

Ranks:
S: Level 3 locks are openable. This means you can open anything. As soon as a single thief gets this, all chests are fucked.

A: Level 2 locks. Until a locksmith gets this, all chests are fucked.

B: Level 1 locks. Until someone gets locksmithing, all chests are fucked.

C: N/A Get a brick.