I can provide for you comfortably and I'll do my level best to be a good husband to you.
There's a breakdown gang doing its level best to get us clear.
But they were doing their level best to save the vessel: that was plain.
If you'll pay me ten dollars a week, Mr. Dart, I'll do my level best to earn it.
But you can be sure that I am bound to do my level best in anything ...