Oh there is a rune that depending on the set will come out sideways & that is actually Brightstave… I belive that rune is 
So anything but it being “sideways” is considered Merkstave for those that read a Merkstave reading. I will also double check that, but I believe it’s that one or it may be Gebo 
because that one sometimes has two “XX” marks together (although I believe they are stacked on top of each other)… I will get back to you on that one.
I would definitely recommend the book by
Those are both great books & the second one is from start to finish any question you may have about the runes & using them. I keep it in my library for reference & make sure that you use the index to jump to different parts of the book if you need to. It’s definitely more for reference than to read straight through.