There is always more to write, but in the meantime here is a short answer I wrote to a similar question from a few months back. The links even have photos!

The long and short - the lines definitely did reach to the beach at Nieuwport in Belgium. The end of the lines were mostly sandbags and concrete bunkers, and raids were conducted from one line to another. It might look vaguely similar to the sorts of Atlantic Wall defenses built around Normandy a quarter century later.