Sub Marine()
On Error GoTo Handler:
Application.ScreenUpdating = False
....
Application.ScreenUpdating = True
Exit Sub
Handler:
Application.ScreenUpdating = True
Stop
End Sub
Application.ScreenUpdating is one of those settings that automatically resets to True on macro completion (so having error handling to reset it is not really necessary). The reason why you see it set to True in so many routines is to adhere to good coding practice.