No pics to hand sry. But yes mounting bracket sandwiches between the towball and towbar arm/plate using the 2 bolts. Rack then slides into a square mounting hole on the mounting bracket.
Top guy and a top quality rack. Best to phone him, even then he can be hard to get hold of as he does some mega miles on his road bike (not bad considering I think he's in his late ish 60's) He runs the business from home so it's not like dealing with a shop etc.
I can't see myself ever having to change this rack it looks like it will last forever. Proper good old fashioned British engineering. None of this plastic and aluminum rubbish.