Where should a drip edge be used?

A drip edge should be installed beneath the underlayment. The purpose of a drip edge is to direct water away from the fascia and into the gutter system, preventing water from seeping underneath the roofing materials. By placing the drip edge beneath the underlayment, you help ensure that water flows over the underlayment and into the gutter rather than under the roofing system, which could lead to water damage and rotting of the underlying structures.

This placement is critical as it promotes proper drainage and enhances the overall effectiveness of the roofing system in shedding water. The other options suggest placements that do not effectively facilitate drainage or protection from water intrusion, resulting in less efficient roof performance and potential for damage.