Skill synergy
From NWNWiki
Some skill work very well together. Having 5 or more skill ranks in one skill will give a +2 synergy bonus when using another skill with which it has a synergistic relationship. Some feats also impart a synergy bonus to specific skills. The synergetic skills in NWN are disable trap and set trap; 5 ranks in either skill will give the synergy bonus to the other.
