A piece of L-shaped metal flashing installed where the downhill face of a chimney — or a horizontal run of wall known as a headwall — meets the roof plane below. Its upturned leg rises against the vertical surface while its lower leg laps out over the shingles, carrying water that sheds down the chimney or wall out onto the roof rather than into the joint. Apron flashing is typically the front, downslope piece of a larger flashing assembly that also includes step flashing along the sloped sides and counterflashing lapped over its top edge. Inspectors may note apron flashing that is missing, too short, poorly lapped, corroded, or replaced with a bead of caulk in place of proper metal — any of which can permit water intrusion at the junction. Related Terms: Flashing, Step Flashing, Counterflashing, Kick-Out Flashing, Cricket (Chimney Saddle)