Advanced Research (Fallout Supplement)
From D&D Wiki
You might not know much about how to use guns and armor, but you sure know how to manufacture and repair it.
Prerequisite: Level 6, Intelligence 16, 5 ranks in Knowledge(Technology)
Benefit: You gain +2 to the Craft (Electronic), Craft (Mechanical), Knowledge (Technology), and Repair skill checks to craft or repair weapons or power armor.