Polyhedra can also share vertices with each other so that more can be made when there are not enough atoms to make isolated polyhedra. This is an example of four octahedra, each linked through sharing single vertices with two neighbors to form a ring. To make four separate octahedra we would need 4 × 6 = 24 vertex atoms. In arrangement with 4 shared vertices, we only need 24 – 4 = 20. When only a single vertex links two polyhedra, they are often described as “corner sharing.”