In Serve layouts work a little differently than they do in Rails. Because there are no controllers to derive layout names from, Serve relies on the directory structure to determine the layout associated with a specific view. Serve layouts are stored in "_layout.erb" or "_layout.haml" files. Serve searches for a layout file in the same directory as the view. If it fails to find one there, it traverses up the directory tree searching each parent directory until it finds the "nearest" layout.
For example, assuming following directory structure:
views/ | A) +-- _layout.erb | +-- index.erb | `-- about/ | B) +-- _layout.erb | `-- index.erb
For "views/about/index.erb" Serve will use layout B. If layout B did not exist, Serve would go up the directory tree and discover layout A which it would use to render the view.
For "views/index.erb" Serve would immediately discover and use layout "A" because it is in the same directory.
So Serve searches up the directory tree for the nearest layout file, and uses that file to render the view. This is convenient because it allows you to structure your Serve project in a way that allows entire "branches" of to share the same layout and "branches" lower down can override the layout used.