I agree with American Pit and Sadie, both good post.
Establish lines tend to produce a type. Even if breeding for performance they will typically have similar physical characteristics.
Some that can be fairly easy for me are jeep or honeybunch, lonzo, may day, colby, OFRN, Villines and boogieman too but sometimes you can be right about a dog being of x line BUT say they are a 50/50 cross you might guess 1 line as it has those physical traits so obviously guessing isn't full proof as the pedigree would tell you its crossed even though you don't see it. I've also seen dogs like 20-25% Jeep (roughly depending on the dog) have the physical type of a jeep dog though again pedigree would tell you it has a fair amount of other blood. And scatterbred dogs at times can pop up looking like a certain ancestor / line though clearly they are a mix of numerous lines.