So I've hit my first stumbling block in the tutorials, during building this helmet. It wants me to use the Border Edge Tool to select the edge to be bridge together, but the edges I need to select just say I cannot select them as they are not border edges. I've been trying to see if  there was anything I was doing wrong or any extra vertexes/edges where there shouldn't be but my brain now needs a rest. I may start over again when I come back to it.