Wood shingles on a roof

Wood shingles are used for roofs but for its a very risky method compare to modern roofing materials we use now... in fixing shingles there is a risk factor for example roofing felt may get a hole while worker screws to timber

After putting the ply Wood fix the roofing felt than screw the 1.5 inch wood batterns to it.. after that start singles with double over layer... 

Make sure the timber batterns are in a equal spacing and the legth of shingles shall cover the nail head to 50mm atleast.