1. Piles of rocks
Known by the more technical term, "cairns," these piles of rock can indicate trailheads or trail direction. These can also be used to mark cautionary areas in the trail system. This seems like an incredibly silly way to mark a trail, but if you hunt or ride in a very large area with no trail markers these small stones can help you remember your way around. Building a cairn is easy: stack stones in a system set forth by you, the builder, so you know what your pattern means. Even laying these out in an obvious place just off trail in the shape of an arrow would be a good start.