All the skill checks, including those for the Thief class, are now rolled on a single six-sided dice. This is a bit of a change for the Thief class, but I prefer the simplicity and since most other checks are done on d6 it made sense (to me anyway) to have the Thief work this way as well. The Hobbit's hiding skill is also changed to d6 for both dungeon and woodland conditions.
D&D traditionally uses roll low for skill checks, but your group might prefer to always have rolling high on a dice indicate success. If you use roll low, you must get that number or less on the dice roll to succeed. If you use roll high, your roll must be at least equal to 7 minus the listed number (eg. 7-1=6, 7-2=5 etc).
Skill Checks - d6
Hear Noises, Find Secret Doors, Find Traps: 1
Find Secret Doors, Find Traps: 2
Hear Noises, Find Secret Doors: 2
Hear Noises, Hide: 2 (5 for Hiding in Woodlands)
Hear Noises, Pick Pockets, Move Silently: 2 (+1 at Levels 4,6,8)
Find/Remove Traps, Hide in Shadows, Pick Locks: 1 (+1 at Levels 3,5,7,9)
Climb walls: 5
The Thief's skills top out at a 5 in 6 chance at level 9, or 83%. This makes them a little worse at climbing walls, but a little better at hiding in shadows than they would be with the default % system.