[BECMI] High Level Thief Abilities
by HåvardFind Traps: Once the character reaches 100%, the Thief can now detect traps automatically. He does not have to declare that he is looking for them. Furthermore he can detect other hidden things if he declares that he is looking for them and succeeds rolling below half of his Thief ability.
Remove Traps: Once the character reaches 100%, the Thief can also remove magical traps at half the chance. This includes sigils etc.
Detect Noise: Once the character reaches 100% with this ability, he can detect invisible creatures. A Successful roll below half his Thief ability means he suffers no penalties to attack such a target. He can also fight in complete darkness with no penalty.
Pick Pockets: Once the character reaches 100% with this ability, he can summon any small non-magical item into his hand. He probably stole it from somewhere.
Move Silently: See Hide in shadows
Hide In Shadows: Once the character reaches 100% with this ability, he can hide in plain sight, effectively becoming invisible until he makes an attack. This will make it possible for him to position himself to use the backstab ability in the next combat round.
Climb Walls: Once the character reaches 100% with this ability, the character takes no falling damage if he rolls below half of his Thief ability.
Read Languages: Once the character reaches 100% with this ability, he can identify magical items rolling below half of his Thief ability
BTW: I'd also consider using the version that Frank Mentzer uploaded here.