Last night one of the players shot me an awkward look when I told him that he could not make Knowledge Dungeoneering check on some important questions in the game because he was untrained in a Knowledge skill.
I can understand this rule for Knowledge Arcana and Spellcraft, but is there a rule for making checks on untrained knowledge skills, like a -4 modifier of something?
Nope. As long as you're not a bard, or have another exception that I am not aware of, all knowledge skills are trained only. What was the question he was trying to answer? Sometimes I allow my players a simple intelligence check to figure out basic things, if they don't have the proper knowledge skill.
Ah yes, thanks Shin, I found it in the PRD.
Untrained: You cannot make an untrained Knowledge check with a DC higher than 10. If you have access to an extensive library that covers a specific skill, this limit is removed. The time to make checks using a library, however, increases to 1d4 hours. Particularly complete libraries might even grant a bonus on Knowledge checks in the fields that they cover.
Oh and it was regarding a monster they encountered. I can't remember the question.
To know something about a monster, you need to pass a DC of 10+CR. Now, based on the rules of rounded (always round down), you could do an untrained knowledge check to call up the strengths/weaknesses of very simple monsters when untrained. For example, a kobold or most wildlife.
This link provides a chart of DCs and can help determine if it is common knowledge or requires knowledge training.
By the way, having a party with a bard, inquisitor, wizard, and druid... it is basically impossible for me to run an encounter that doesn't start with me practically handing them the Monster Manual, heh. All the knowledges and most with bonuses when determining monsters.
If you're using the Beginner Box, the rule about untrained skill checks is at the bottom of page 34.
Thanks guys. Although I love the Beginner Box rules, I think we'll use the unskilled DC10(+CR) check as a house rule for simple questions and keep my players happy.