How do you install roof open valley?

You need to start by running a piece of ice and water shield 36" wide up the valley against the wood, then run felt on the shorter rafter side and lap past the valley 12"-18", now run the felt on the other side and cut in the valley with a hook blade careful not to cut through bottom layer of felt. now run a metal valley piece up the valley if using more than one piece start at the bottom. now run your shingles past the valley center all the way up now chalk a line 3 inches from the center of the valley and cut again with hook blade, careful not to score the metal. now repeat the on the other side. you should use a metal valley with a "v" bend in the metal to slow water from rushing under the shingles especially if the pitches are different.