Dogbone (dumbbell)

The dogbone consists of two return loops at the ends, joined by a seemingly double-track section — from above the shape recalls a bone. The trick: the “double-track main line” is really one long round trip. Hide the loops (e.g. in tunnels) and the layout reads like a genuine point-to-point line. Because each end loop is a true reversing loop, it needs reversing-loop wiring in a two-rail system.