What does Judges 12:5 mean?

The Gileadites captured the fords of the Jordan River leading to Ephraim. Whenever a fugitive from Ephraim tried to cross, the Gileadites would ask, Are you from Ephraim? If he said, No, Judges 12:5 - Modern Text Bible

(Gilead controls the river crossings, trying to catch fleeing Ephraimites by questioning them.)