ξύλον ἀγκύλον οὐδέποτ' ὀρθόν → a bent board is never straight
prep.
Except: P. and V. πλήν. Failing this: P. and V. εἰ δὲ μή. Best of all, let us make terms for ever. Failing that . . .: P. μάλιστα μὲν εἰς ἀΐδιον συμβῶμεν, εἰ δὲ μὴ . . . (Thuc. 4, 63).