◇ Just read — no move neededPatrolling the bank
A cannon parked on its own river bank (rank four) is the river-patrolling cannon (巡河炮). The chariot chapter gave this same bank to the chariot as the 巡河车; the cannon takes the lane for the same reason — total mobility without commitment — but it hunts differently: at range, through screens. From the bank it slides to either flank and snaps up crossed enemy pawns through whatever screen offers itself, pawn after pawn, without ever leaving home.