At the rake the sealant strip will be positioned at the outer roof edge and once warmed by the sun it will help seal the rake ends of all the finish roof shingles.
Roof shingle cellophane strip.
Gaf mastering the roof chapter 09 this video demonstrates the proper installation technique for gaf starter strips.
This prevents the shingles from sticking together when storing and shipping bundles to the work.
To prevent shingles from sticking to each other while still in the bundle manufacturers add a small strip of cellophane on the back of each shingle.
A simpler and very useful purpose for using starter shingles along the rake edge is that it gives the installer a nice straight line to use as a guide when ending each course of the field shingles.
Many self taught roofers follow the wrong technique of installing the first row.
The starter shingle if you put the first row of shingles on the edge of the roof just like all the rest you will see the bare roof deck through the cracks between the shingles.
A superior alternative to starter shi.
This article discusses best roofing practices for the installation of asphalt roof shingles including installation temperature shingle sealing methods shingle course offsets asphalt shingle nailing location and specifications low slope and steep slope limits for asphalt shingles and roof flashing at building eaves and around skylights.
For an overview on changing the roof or roof covering on a house and special information on mansard roof shingles follow this link.