What is a rail flip charge?

I'm curious, could you please explain what exactly is a rail flip charge in the context of cryptocurrency transactions? I've heard the term mentioned but I'm not entirely clear on its meaning and how it impacts the overall transaction process. Is it a fee associated with a specific type of transaction? Or perhaps it's related to a specific blockchain protocol? I'd appreciate it if you could provide a clear and concise explanation of the concept, including any potential implications for traders and investors.