You can use a straight edge to achieve a straight cut.
How to shingle a roof valley video.
Nail down each valley shingle at least two inches 50 mm back from the chalk line.
When you reach the valley lay the shingles over the valley and trim the edges to the chalk line.
The open woven and closed cut methods are demonstrated.
Gaf mastering the roof chapter 12 this video demonstrates the proper installation technique for installing roofing valleys.
As shingles are installed on the adjoining roof area the end of each course of shingles is trimmed cut 2 back of.
Over driving nails is always a.
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.
The most common closed valley is a closed cut valley where shingles are installed on the entire roof area on one side of the valley first with each shingle course extending at least 12 through the valley centerline.
This video demonstrates the proper installation technique for installing roofing valleys.
Begin to install roof shingles on either roof face.
The open woven and closed cut methods are demonstrated.