Maybe the intention is that the thief has the listed percentage chance of picking the lock, then if they fail they make the same check that anyone else would.
However, whatever the intention, it isn't clear.
That was the intention and as many have pointed out. Why make two die rolls when you can just give a bonus to a single die roll?
I would have never thought that to be the case.
So, a thief would roll d% to sneak silently and hide in shadows, with success indicating a complete success that couldn't be opposed (per the 3rd paragraph on p.27.) If he failed, then he would make normal skill checks, opposed by the enemies?
Actually, having two separate systems for thief skills and skill checks is one of the oddities that really jumps out at me. It looks like anyone can make a sneak or hide check (halflings even get a bonus!)
Plus, the skill check rules on pp.52-53 seemingly contradict themselves:
-Under Difficulty Levels there's an example of a static
DC 10 skill check to hear "the approach of a cautious footpad."
-But the Opposed Skill Checks paragraph, in conjunction with the SKill Checks for Commom Activities, suggests that Sneaking (Agility) would be opposed by Luck (Listening) and Hiding (atribute?) would be opposed by Searching (Intelligence.)
I was about to ask "what exactly does 'sneaking entail?" but I found my answer in the Halfling entry:
Sneaking is actually "sneaking silently" and Hide is "hiding in shadows."
I think those need to be expressly differentiated in the Skill Chapter so that one does not misconstrue the generic 'sneaking' to be the sum of moving while hiding. What attribute is Hiding based on? Agility? Intelligence?
For that matter, couldn't Sneak cover both and you could just remove references to Hide (the generic skill, not the thief skill)? Then Sneak (Agility) could be opposed by Search/Spot (Intelligence.) I bring that up because if you have to roll to sneak and roll to hide, would the opponent then make a search roll and a listen roll? That's 4 rolls (not counting thief skills) to determine if a character can remain undetected while moving silently in the shadows.
One of the things that drew me to DCC is this marketing promise: "Adventure as 1974 intended you to, with modern rules grounded in the origins of sword & sorcery."
However, there is nothing modern about having a secondary skill system for a class that functions completely differently than the base skill system, and with no guidelines on how the two interact. Also, the DCC skill check system is very weak compared to any AD&D retro-clone that has one.
1) Only have one skill system. A thief's abilities should augment the basic system, not be entirely different.
2) Combine 'sneak silently' and 'hide in shadows' into just 'sneak' or 'stealth.' The separation is clumsy and unneccessary. There's no point in hiding if you can't be quiet, and there's no point in being quiet if you can't remain unseen.
3) Clearly define the interaction/oppositions between sneaking & listening and hiding & searching (or in line with #2 above, 'sneak' & 'perceive.')
4) The more esoteric thief abilities (pretty much everything that thieves can do that could not be attempted with a regular skill check (sneak, hide, climb) could justify the unique (old-school throwback) d% rolls since they don't clash with the skill system.
Whew, that was a big first post!