I find it puzzling. Perhaps it will help if you give us the source (title and author), plus a link if possible. Also, you might include what came before the text you quoted (you're allowed to quote up ti four sentences).
If you thing about the United States, it has coasts on the east and west (the Atlantic and the Pacific) and borders to the north and south (Canada and Mexico). Normally people just say "coast to coast" to mean "all across America," but this author has chosen a more emphatic phrase to say that he was engaged in litigation all around the country.
thank you both but it is still puzzling for me, this sentence from "life code by Dr Phil" and here is the context: "thank you to bill dawson, my trusted friend and "foxhole buddy", for encouraging me to always search deep into my thoughts, feelings, and experienced as we "fought them off" together in courthouses coast to coast and border to border.
Your thread title is "coast to coast and border to border". Glenfarclas explained in post #3 that to mean "all around the country". That assumes the country is the US. It's equivalent to "from east to west and from north to south".