Flats come in three types, a
1. expanded flat
2. regular dflat
3. running flat
Here, I will describe the running flat, which has the following characteristics:
1. running, 3-3-5 flat wave
In a running flat, wave B stops beyond the start of wave A, and wave C falls short of stopping near the end of wave A. The difference between an expanded flat and a running flat is where wave C ends. In an expanded flat, wave C terminates beyond the end of wave A. The appearance of a running flat is considered rare.