Types 2

Range lights are used to indicate a safe passage inside channels, and recommend a course where navigational hazards are present on both sides.
Usually they come in pairs and are situated in such a way that one shows over the other when they are in line.
The light close to the observer is called the front light and the light behind is called the rear light.
For example, to navigate safely in a channel with range lights, the front light must be in line with the rear one. If they are not in line and the front light is on the right side, then you are off course and on the port side of the line.
If the front light is on the left side, then you are off course and on the starboard side of the line.
During daylight a range consists of a pair of beacons, and lining up those beacons is similar to lining up the lights.