the phrase first/second fix applies to most trades and if you look at what you have written and use as a comparison then you have virtually answered your own question
first fix brings a supply to a certain position but does not allow for termination or connection
i would,nt say you have got it wrong but there is a big, big learning curve with the buiding trade and more experienced people than you get it "wrong" every day
holyrood, british library, wembley, T5 heathrow to name but a few. in our own homes it just feels so personal though
and definately hurts the wallet. good luck