Amateur's Pride (3.5e Flaw)
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"If you can make fire with a couple of sticks, I can pick locks with sticks." -Amateur Rogue speaking to a Ranger.
Prerequisite: Must have at least 4 ranks in any craft, open lock, or disable device skill.
Effect: Due to a lack of formal training your character suffers from a -2 penalty to all craft checks, pick lock checks, and disable device checks. On top of this penalty your character is unable to make use of any tool or kit that grants them an opposed bonus against a normally penalized skill check, including masterwork items. Effectively your character must use improvised tools at all times making them unable to use Artisan's Tools or Thieves' Tools.
Roleplaying Ideas: "Back in my day we didn't have any fancy hammers and anvils. We had to make everything using rocks, uphill both ways!"