I was reading the Manual, as I usually do before I start a new CRPG, and found that Open Locks or Disable Traps isnt restricted by any class, specifically there is stated Classes: All.

I began to play as a Wizard and found out that I wasnt able to neither open locks nor disable traps. Then I decided to google some info and then it came, according to info on the internet, Open Locks and Disable Traps can only be executed by Rogue or Assassin.

Am I doing something wrong or the manual has really wrong info?

For Open Locks, you just have to have enough skill points in it to allow you to beat the DC of the lock itself. You can bump this up by casting Dex buffing spells, or using thieves tools if you have them.

For Disable Traps, any character can if they have the skillpoints invested in it, however you won't be able to disable any traps with a high DC unless you have a class that has the Trapfinding ability like the Rogue.

Some work arounds for a wizard is to use the Knock spell to unlock things (2nd-level spell), and Find Traps to disable traps (3rd-level). Both are area affect spells. If you have the Pixie familiar, it will generally have rogue levels, and points in Open Locks and Disable Traps.

You have to put skill points into open locks/Disable traps on level up. If you have no points at all, you can't even attempt to open locks. Once you put at least 1 point in, it will let you attempt to open a lock and tell you how much you failed/succeeded by.

For a wizard these are "Cross Class" skills. Which means they cost twice as much.