Hike trails that have no set path can be challenging. Generally when on a trail without an obvious route, people will stack rocks like these. This is called a cairn. I took a photo of a big one on the Chilkoot Trail a few years back.  If there are trees, someone will often tie some survey tape along the route. Sometimes finding a trail can be an adventure as you follow these "signs" and hope they lead to where you are intending to go.