Chimney flashing, which is usually made of copper or aluminum, seals the joint between the chimney and the roof. It protects the joint against leakage from rain or melting snow. If constructed properly, it accommodates slight movement between the chimney and the roof. Flashing a chimney requires several components. First is the base flashing, which is installed on the lower vertical face of the chimney. It covers the front and wraps around the chimney sides. Then it comes the step flashing, which is bent up along the side of the chimney. This is covered by the cap or counter flashing, which is set into the chimney mortar joints and bent over the step flashing. The counter flashing may follow each individual mortar joint and step its way down the side of the chimney, or it may be set into a groove cut in the chimney side called a reglet. The advantage of using the reglet is that it allows a single piece of counter flashing.