Aside from the details of how you assemble the bolt hardware Andy, there are three things to remember. First, the blade attaches to the underside of the mounting disk ("blade plate"), not the upper side. Second, the blade has its straight (cutting) edge toward the forward direction, and its tilted (air/grass deflecting) edge trailing. This means the bend of the deflector is always upward, never downward. If the deflector is downward, it will cut and push the grass down way below the cutting height, and that will make it drag on the ground. It also probably won't cut grass well because the deflector edge is blunt. Third, the flat or slightly rounded head of the attaching bolt is always downward, with the nut at the top, above the blade plate.
Much more important than any of that, is assembling the hardware properly so the blade doesn't come off. That could have extremely nasty consequences, including fatality.
