The nutcert plate is a thick steel plate that goes inside the frame rails and has 6 or 8 nuts welded to it. What it does besides giving you somehting to bolt to is it spreads the load across it's length and sandwiches the frame rail between so that the frame rails don't get ripped out. Even the cheap receivers need to be bolted that way though some give you some fancy nuts that you fish thru the frame but thats pretty weak IMO. No way round it, you need those plates to get started and they are pretty much a dealer OEM item, I hope they are still available and were not one of those items jeep firesaled when they stopped production of the XJ, they did that with almost all the other XJ add on's and unlike the front hook brackets I don't know anyone who makes rear ones though you could make them yourself if you had a left and right for a template, you could use alot heavier steel and drill and tap the holes directly.