Flashings are used to seal the opening where the chimney penetrates the roof and to divert rain and snow down from the roof and away from the chimney system. A series of adjustable flashings are available depending on your roof pitch. A flat and low pitch flashing is used to seal flat and low pitch roof (up to 2/12 pitch) openings. To determine your roof pitch, measure the number of inches from the end of a level ruler down to the roof. A flashing 0/12 to 2/12 pitch the base is 27 3/4”. A flashing for a 2/12 to 6/12 pitch has a base size of 31 7/8”. For 6/12 to 12/12 pitch the base is 31 7/8”.