You need IKO nails to fix the underlayment and roof shingles. 
Corrosion resistant nails (galvanised clout nails) 25 mm in length and a head diameter of 10 mm. The shaft should be 3 mm in diameter and barbed.
The nails should sit 19 mm into the roof surface.

Laminated shingles (Cambridge Xtreme 9.5° or Cambridge Xpress) and nailing of hips and ridges require nails 30 mm in length.

Proper fastening is essential for a good roof. Drive the nails straight so that the nail heads are flush with, but not cutting into the shingle surface. Always nail 2,5 cm above the cut-out and 2,5 cm from each edge. For correct positioning and nail quantities per type of shingle and roof slope check out the detailed application instructions.

If your roof has a steep slope (>60°) or if you are living in a highly exposed area you will need to use extra nails and Shingle Stick adhesive.