αὐτὸν κέκρουκας τὸν βατῆρα τοῦ λόγου → you have struck the very threshold of the argument, you have struck the most important and chiefmost point
Ar. and V. ἀμφήκης, V. δίστομος, δίθηκτος, ἀμφιπλήξ, ἀμφιδέξιος.