One long stroke, and you can hear it when you're cutting the knife.

一长一划，切刀时都能听到。

Then he doubled one end of a strap around the little piece of wood, and with his knife cut round holes through the strap.

然后， 他将一根带子的一端绕在这块小木头上，并用他的刀在带子上切出圆孔。