To secure the roof valley flashing nail it down carefully.
Shingle roof valley installation.
The open woven and closed cut methods are demonstrated.
This video demonstrates the proper installation technique for installing roofing valleys.
How to do it determine cuts.
Ensure ice and water protector has been installed along the valley first.
Some roofers cut the shingles parallel to the flashing s center ridge.
Only nail at the edges with only enough nails to.
I then move the shingle to the uppermost course on the roof plane line up the mark on the shingle with the valley center and again mark the corner.
Others start with a 3 inch wide.
Place a piece of sheet metal under the shingles to make sure you will not damage the flashing.