MD 806 begins at an intersection with US 15 (Catoctin Mountain Highway) and Auburn Road, the old alignment of US 15 that heads south closely paralleling the southbound lanes of US 15. The state highway, officially MD 806A, heads north as two-lane undivided Catoctin Furnace Road through the community of Catoctin Furnace. MD 806 parallels the northbound lanes of US 15, which itself parallels the eastern edge of Catoctin Mountain and the eastern boundary of Cunningham Falls State Park. The state highway crosses Little Hunting Creek and passes the site of the Catoctin Furnace and the Catoctin Wildlife Preserve and Zoo. Just south of the zoo, MD 806 has access to US 15 and the Manor Area of Cunningham Falls State Park via a two-way spur to US 15, which closely parallels MD 806 at that point. The state highway veers away from US 15 and intersects Blue Mountain Road, which heads west as unsigned US 15G to provide another access point to the parallel divided highway. MD 806 traverses High Run then reaches its northern terminus at the southern town limit of Thurmont.