The effort requires at least a simple tool of the appropriate sort (a pick, pry bar, blank key, wire, etc.). Attempting an Open Lock check without a set of thieves' tools carries a –2 circumstance penalty, even if a simple tool is employed. The use of masterwork thieves' tools enables the character to make the check with a +2 circumstance bonus.

Check: Opening a lock entails 1 round of work and a successful check. (It is a full-round action.)