Before installing the top rack, make sure that the grate with protruding ends is facing the front, near you.
Also, ensure that the edges of the rack are curved upward.
Stand in front of your Pit Boss, hold the grate in the middle, and turn it diagonally, going from one corner to the other.
Insert it into the grill at this angle. It will fit snugly inside the grill.
Once the top rack is fully inside the grill, slide it all the way to the side that is higher. For example, if the left side is higher, slide it all the way to the left. Make sure that the front protruding ends are forward enough to clear the side ledges of the grill.
Bring the rack up and then back and down so that the protruding ends on both sides fit into the designated cutouts on the ledges.