Thieves have a pretty good chance at climbing walls, and that is a good thing. My qustion pertains to whether or not they need climbing aides to do it.
Under the thief class it says:
"Climbing Walls: Thieves are adept at scaling sheer surfaces, including walls or steep cliffs. They require a proficiency throw for each 100’ they intend to climb. If the roll fails, they fall a distance equal to half the attempted distance, plus the distance covered by any previous throws, taking 1d6 points of damage per 10 feet. Thieves climb at ¼ their standard combat movement rate. "
This makes no reference to if tools are needed or not.
Under The climbing proficiency though it says:
"The character can climb cliffs, branchless trees, walls, and other sheer surfaces, without climbing aids, as a thief of his class level."
To me this implies that as long as the thief is using tools, like ropes and pitons and the like he or she has no chance at failing while climbing? Is this the same for every adventurer?
I believe this is the intent: climbing gear negates the need to use the climbing proficiency. That's strictly for free-hand climbing.
In my own games, I added the wrinkle that people without the climbing proficiency using gear to climb will do so at "Exploration speed", meaning a heavily armored fighter trying to safely climb a 50' rope will take the better part of 10 minutes to do so. Since there's a limit to how many people you can put on one rope, this made climbing represent a distinct danger of monsters wandering in while your party was divided, but thieves and climbers could quickly get to wherever the action was.
I'm not an Autarch, but I visualize thieves as climbing more or less like a monkey, a mountain-goat, or like certain video-game characters (Nathan Drake, or the Assassin's Creed protagonists come to mind). So far, my rule of thumb is that if one of those guys could climb it, a thief could too. A thief could climb using loose/degraded bricks, tiny cliff outcroppings, corners, windows, decorations, etc, can shimmy up pipes and tree-trunks, and can make short leaps between such holds. He is not spiderman and ultimately needs something to work with, but there almost always will be something.
My reading is that thieves only need to roll if they want to climb 100+ feet all at once, meaning that most of the time they do not roll and simply climb at their speed, so climbing equipment generally is not necessary for them. If a thief was to use proper climbing equipment, then he could climb any distance without needing to roll.