Originally Posted by
Fentuz
With that flat i call it a U and the fact that the ones I saw bottom on the flat, not one the taper… wear and tear. if it was a proper dovetail feature it would be different
I am sorry, but you are wrong: only the two sides are in contact with the frame and they are tilted so that they avoid any gap/play. The center flat part isn't in contact with the frame.