I started to hook a set using the last dolly on the yard. It was one of the older red type of dollies. I noticed that someone had bent the 5th wheel release arm, no wonder that it was the last dolly on the yard. Whoever did it not only bent the release arm but also managed to tear off the metal flap that rotates down and covers the top part of the release arm, when the release arm is retracted due to being hooked around a kingpin. You usually have to move the flap out of the way to pull and lock the release arm out. It looks like it was designed as a safety feature, looks are deceiving. I was wondering if this hook was going to be safe without the metal flap but then it occurred to me that the red dolly fifth wheel is the same, looks the same to me, as the fifth wheel on most of the gray dollies and most of the tractor fifth wheels. The flaps on those units are not the same flat design, that you find on the red dollies, but are cut at an angle. Those angle cut flaps couldn't be a safety feature because they couldn't stop the arm from releasing in the event of some kind of failure of the fifth wheel. What is the purpose of the flap? Apparently, Saia doesn't consider the flap a safety feature because the company has been buying equipment with the angle cut flap for years. I asked a very experienced shop mechanic what does the flap do, and he said, I don't know it's just there. So, know I am asking you? What does the flap do and if it is not there, what does the DOT do about a missing flap if you get inspected.