How do weave mazes work?

Some paths cross: the way goes straight over a bridge or straight through the tunnel beneath it, and never turns on a crossing. How to play explains it. Weave mazes are always drawn as pipes, so the bridges show ("How the walls are drawn" is greyed out for them), and they are always carved the same way, whatever "How the mazes are carved" says, because their crossings are laid first. The solution shows the way going over or under each crossing.