Most mouting solutions do just have the plate screw into the case, but it is all about how they do it. Tray mount means that the plate is lowered into the case and attaches to 5 standoffs located on the inside of the case. Top Mount means that the plate is put into the case through the bottom and the plate screws into the top "bezel" from underneath. Sandwich mount has the plate "sandwiched" between the top and bottom portions of the case.