Petroglyphs are carvings in stone made by native people. The carvings in track rock were created by different people over many years. This is why it is common for carvings to overlap. Each carving tells the story will represent significant events to the person who made it.
A modern according of the carvings on track rock boulder (see picture)
The serrated edge shown here may have been made as the result of someone repeatedly rubbing the same area to create the rasping sound. (see picture)
Plaque courtesy Lat34North.com.
Original page, with additional info, here.
Photo credit: Byron Hooks of Lat34North.com.