Book Knowledge - Thieves Tools

You have become proficient in thieves tools.  This includes the very basics of:

• basic lock design
• finding the tools needed to work on a lock
• using tools of the trade to unlock basic locks
• disarming traps of basic design
• other checks where tools such as these might be used.

You have spent some time reading a book, or several books, that might teach your character a basic skill.  You know the basics of a skill, to the point that you feel you can accomplish the tasks associated with it.  However, this is purely book knowledge and doesn't teach you about things that a person does not normally encounter.