When they had laid (epithentes). Second aorist (constative) active participle of epitithēmi, to place upon.
Many stripes (pollas plēgas). The Jewish law was forty stripes save one (2Co 11:24). The Roman custom depended on the caprice of the judge and was a terrible ordeal. It was the custom to inflict the stripes on the naked body (back) as Livy 2.5 says: “Missique lictores ad sumendum supplicium, nudatos virgis caedunt.” On plēgas (from plēssō, to strike a blow) See note on Luk 10:30; and notes on Luk 12:47.
The jailor (tōi desmophulaki). Late word (desmos, phulax, keeper of bonds), in the N.T. only here (Act 16:23, Act 16:27, Act 16:36). The lxx has the word archidesmophulax (Gen 39:21-23). Chrysostom calls this jailor Stephanus, he was of Achaia (1Co 16:15).
To keep safely (asphalōs tērein). Present active infinitive, to keep on keeping safely, perhaps “as dangerous political prisoners” (Rackham). He had some rank and was not a mere turnkey.