A skill check represents an attempt to accomplish some goal, usually while under some sort of time pressure or distraction. Sometimes, though, a character can use a skill under more favorable conditions and eliminate the luck factor.
Taking 10: When your character is not being threatened or distracted, you may choose to take 10. Instead of rolling 1d20 for the skill check, calculate your result as if you had rolled a 10. For many routine tasks, taking 10 makes them automatically successful. Distractions or threats (such as combat) make it impossible for a character to take 10. In most cases, taking 10 is purely a safety measure —you know (or expect) that an average roll will succeed but fear that a poor roll might fail, so you elect to settle for the average roll (a 10). Taking 10 is especially useful in situations where a particularly high roll wouldn’t help (such as using Climb to ascend a knotted rope, or using Heal to give a wounded PC long-term care).
For example, Krusk the barbarian has a Climb skill modifier of +6 (4 ranks, +3 Strength modifier, –1 penalty for wearing studded
leather armor). The steep, rocky slope he’s climbing has a Climb DC of 10. With a little care, he can take 10 and succeed automatically. But partway up the slope, a goblin scout begins pelting him with sling stones. Krusk needs to make a Climb check to get up to the goblin, and this time he can’t simply take 10. If his player rolls 4 or higher on 1d20, he succeeds.
Taking 20: When you have plenty of time (generally 2 minutes for a skill that can normally be checked in 1 round, one full-round action, or one standard action), you are faced with no threats or distractions, and the skill being attempted carries no penalties for failure, you can take 20. In other words, eventually you will get a 20 on 1d20 if you roll enough times. Instead of rolling 1d20 for the skill check, just calculate your result as if you had rolled a 20. Taking 20 means you are trying until you get it right, and it assumes that you fail many times before succeeding. Taking 20 takes twenty times as long as making a single check would take. Since taking 20 assumes that the character will fail many times before succeeding, if you did attempt to take 20 on a skill that carries penalties for failure (for instance, a Disable Device check to disarm a trap), your character would automatically incur those penalties before he or she could complete the task (in this case, the character would most likely set off the trap). Common “take 20” skills include Escape Artist, Open Lock, and Search.
For example, Krusk comes to a cliff face. He attempts to take 10, for a result of 16 (10 plus his +6 skill modifier), but the DC is 20, and the DM tells him that he fails to make progress up the cliff. (His check is at least high enough that he does not fall.) Krusk cannot take 20 because there is a penalty associated with failure (falling, in this case). He can try over and over, and eventually he may succeed, but he might fall one or more times in the process. Later, Krusk finds a cave in the cliff and searches it. The DM sees in the Search skill description that each 5-foot-square area takes a full-round action to search, and she secretly assigns a DC of 15 to the attempt. She estimates that the floors, walls, and ceiling of the cave make up about ten 5-foot squares, so she tells Krusk’s player that it takes 1 minute (10 rounds) to search the whole cave. Krusk’s player gets a result of 12 on 1d20, adds no skill ranks because Krusk doesn’t have the Search skill, and adds –1 because that is Krusk’s Intelligence modifier. His roll fails. Now the player declares that Krusk is going to search the cavern high and low, taking as long as it takes. The DM takes the original time of 1 minutes and multiplies it by 20, for 20 minutes. That’s how long it takes for Krusk to search the whole cave in exacting detail. Now Krusk’s player treats his roll as if it were 20, for a result of 19. That’s good enough to beat the DC of 15, and Krusk finds an old, bronze key discarded under a loose rock.