The skylight trailing edge must allow for the rear wing spar bolt to be inspected/removed.
Skylight at rear wing spar bolt
The hole allows enough room for a thin wall socket to reach the bolt.
Cutting the corner in works as well.
The bolt may be hidden under the turtledeck-to-wing fairing.
The level of the turtledeck here is lower than the bolt head. Note the gap along the skylight trailing edge.