Ducati Diavel Carbon ABS Owner's Manual page 158

Refit the left cowling (1, fig. 149) as follows:
E
start the side screw (2, fig. 149) retaining the electrical parts
box in its thread;
start the top screw (3, fig. 149) retaining the electrical parts
box in its thread;
start the bottom screw (4, fig. 149) retaining the central
cowling in its thread;
3
1 2
4
fig. 149
157