Advanced Ranger Trap

Your ranger traps are especially difficult to notice and avoid.

Prerequisite: Trap class feature, ranger level 5th.

Benefit: Add +1 to the Difficulty Class on all Perception and Disable Device skill checks to find or disable the traps you make with your trap class feature. Add a +1 to the Difficulty Class on all saving throws against the effects of the trap you make with your trap class feature.

Source: Ultimate Magic