What should you consider when planning to replace the flights in your rectangular clarifier? Flights are also known as scrapers, c-channels, flight boards, drag flights, and sludge pushers. Regardless of what you call them, they serve the same purpose. Flights convey settled solids to a hopper or collection pit and push surface debris into a scum removal device in a straight-line clarifier system. Although flights may all seem the same at first glance, there are some key characteristics to think about when evaluating which type you may need for your chain and scraper system.