The Arianespace technician is finalizing the seam between the fairing and the Ariane 5 launcher.
This interface is composed of 420 bolts which hold the fairing onto the launcher.
Once the launcher reaches an altitude where the air density will not damage the satellite, the fairing is separated longitudinally along the slice line.
This splice line has an explosive device that allows the fairing to “peel away” as the launcher approaches the frontier of space.