This pattern is for the dogs who everyone claim should be a size Large, but aren't. My Labrador Murphy is a bit larger than anything labeled "Labrador" sizing. This pattern was designed to fit him and other dogs with a neck around 19-20 inches and a chest of 36-38 inches. He measures 36 from collar to tail as well and this sweater is designed to stop just short of his "bum".
It's also shaped so that they can run around outside and do their business without getting anything on the sweater. If you follow the yarn recommendations it will also be machine washable and dry-able.
Its pretty simple with explanations for anything more difficult than a knit or a purl written out.