Trapper’s Setup

You have an instinct for waiting until just the right moment to spring a hazard or trap.

Prerequisite: Craft (traps) 5 ranks.

Benefit: When you manually trigger a trap against opponents, that trap receives either a +2 circumstance bonus on melee attack rolls or a +2 circumstance bonus to its saving throw DC. ® ™ 538 68 538 69

Source: Ultimate Combat