Attached to the C15 smokebox side is a Westinghouse pump, a common feature amoungst Highland engines.
The kit makes provides a couple of whitemetal castings and some rough instruction for fitting. Not being familiar with this fitting I looked at photos and concluded that they were bracketed to the appropriate bit of engine and most importantly, held vertically in all directions. If you just fit the bits then the pump will lean as the smokebox at this point isn't vertical.
Making up a spacer from spare etch wasn't too difficult but I still didn't have much guidance on the plumbing. In the instructions there is a side view but it doesn't make it clear where the top pipe goes in. I took it around the back of the disk on the top of the pump which is probably correct, although having seen a real Westinghouse, I'm not so sure now !