Acquiring non-class skills for which untrained checks aren't allowed after character creation

Question

I have a Paladin, now level 2, and at character creation, I didn't exactly have a ton of skill points to set. I have -1 in INT and I'm not a human, so that left me with quite little choice. This campaign has only my character and a druid (plus his wolf).

At one point, we came across a prison cell in an underground cave-building-thing with a ghoul and, most importantly, a chest and a bookcase in it. We shot the imprisoned ghoul down and then looked for the key to the cell, without success. The bars were thick, solid metal and they came out of solid rock. After trying to destroy the lock's mechanism, it became clear we could not force our way in, and we left, frustrated, since that prison cell would have contained the only treasure the whole dungeon had.

Then we knew that lockpicking (Open Lock skill) would be very useful. After all, not all doors will conveniently be easily broken wood and a locked metal box would screw us over. I looked everywhere I could, but I did not find a way for me to learn Open Lock, a non-class ability for which untrained checks aren't allowed.

I have two questions regarding this:

1. Assuming I had at least 10 in INT and thus would get 2 skill points per level instead of 1, would it be possible for me to suddenly put a skill point in Open Lock? If so, my druid companion could learn the skill since he gets 2 or 3 skill points per level (not sure how low his INT is). How could that be justified in a realistic way, since there's no master rogue to teach him magically as soon as he reaches level 3?

2. In a situation where you only get one skill point per level, is there a way, any way, to become capable of opening locks without a key? Could I find an expert in town who could somehow teach me basic ability (thus making the skill one in which innate tests are allowed for me) regardless of my inability to put points in the skill?

Additional note: For now at least (the DM will see when we reach higher levels), we're not using any "add-on" books. Only the master's, player and monster books. And maybe an extra monster book or two, not sure, that's a mystery that stays behind the master's screen.

Don't hesitate to ask for more information in the comments. We're playing in French, and many game terms vary wildly between the original English version and the French translation (just look at the armor list for instance), so I may have made up stuff there.

Answer 1

In short, you may invest one skill point or odd number of skill points for an untrained cross-class skill. You have only half(1/2) rank for that skill. Mechanically, you don't have any advantage over untrained ones, but in your next level, you can invest one more skill point in the skill, making that a trained skill so that you are allowed to try the skill.

For justifying how exactly did you get the appropriate training, the Player's Handbook or SRD says nothing about justification in role-playing aspects. You simply get the skill points, and justification is up to you. You can say that you analyzed broken locks' structure by taking a glimpse at it, got a bobby pin and practiced with it so many times, or you suddenly became an apprentice of a rogue. Oh, you are a paladin, so maybe your deity have taught you with the necessary skills in your dream!

P. S. As @KRyan have said, the appropriate skill name for your intended action is "Open Lock". Be sure not to confuse it with "Disable Device", which is for trap jamming!

Answer 2

In general spending skill points on Open Lock is a bad idea because the DCs are very high and there are easy ways to bypass those skill checks without even rolling (e.g. knock). This is even more true for your characters, who get very few skill points. You don't need skill points, you need

gp:

Crowbar(2 gp): +2 circumstance bonus to opening things via strength checks

Sledge(1 gp): "good for smashing open treasure chests" (PHB, pg 127, YMMV)

Divine Scroll of Knock (150 gp): Your druid can read this without rolling. Opens all the things. As a note, this is a very hard item to create as a divine caster, especially with access only to core materials. Your GM may rule that it is more expensive than normal.

Large Bag of Holding Type IV (20,000 gp): Just stick the offending chests in the bag and deal with them later.

-or-

xp:

Stone Shape (drd 3): Gets past stone doors, walls, and chests, if those were an issue.

Rusting Grasp (drd 4): Say bye-bye to all your metal-related problems.

Leadership (Feat, Character lv. 6): Grab a LG rogue or sorcerer/wizard as your cohort, and have them open the locks.

Answer 3

Each level, you may spend your skill points any way you like, regardless of how you have spent them in previous levels, so long as you respect the rank maximums (level+3 for class skills, half that for cross-class). So yes, you may put points in Open Lock even if you never have before.

That said, as a cross-class skill, each skill point you put in Open Lock only gets you ½ a skill rank. You don’t count as trained until you have at least 1 rank,¹ so that’s a minimum of 2 points.

As a paladin, you also likely have poor Dexterity. Between poor Dexterity and few ranks, you are very unlikely to actually succeed on Open Lock checks.

¹ per SRD > Skills > Skill Descrptions:

Trained Only

If this notation is included in the skill name line, you must have at least 1 rank in the skill to use it.

Untrained

This entry indicates what a character without at least 1 rank in the skill can do with it.

Answer 4

In terms of the rules, there is nothing to stop it happening. Unlike some RPGs, DND does not rely on a system of "you must try to use a skill to make it improve". Nor does it have a lot of rules that would add to the complexity of the game without adding much value. I have never had the DM turn around and tell me my character has got the flu, and there aren't really rules to cover it, so the DM is expected to make house rules to cover such things that will take the game in the direction you want it to go. If you want more complexity and realism, add it in yourself, or ask advice on house rules on this site.

Answer 5

In the player's handbook on page 62 there are guidelines for gaining skill points and how to spend them. One of the notes under Skills at Higher Levels says:

4.If you want to pick up a new skill for your character, you can spend skill points equal to his or her character level +3. These skill points buy 1 rank each if the new skill is a class skill or 1/2 rank each if it’s a cross-class skill.

This seems to say that at higher levels in order to put points into a skill you must max out the skill. This interpretation is based off the fact that it does not say you can spend up to your character level-3 skills points, and the wording of the previous step regarding putting points into skills that are not maxed out which says:

You may spend the number of skill points it takes to max out the skill, provided that you have that many skill points to spend.

This is likely to represent a character who does not gain many skill points being unable to learn new skills as easily as he is able to maintain the skills he already knows.

Personally, in my group we do not use this rule.

I would discuss it with your DM, although he is likely to say it would not make sense and would be like Deus ex Machina with the character suddenly having the perfect skill to get out of the situation when he had never displayed it before.

Also as a side note, I'm guessing neither of you happen to be carrying thieves tools on the off chance you decide to pick the skill up later, so there would be a penalty to the skill checks.