As it was presented in the OP, I don’t think it is a shape. If I get two squares and stick them next to each other so one side of each is touching, have I suddenly got one rectangle? Or do I still have two squares with a border between them?
Someone else posted an amended version with the internal lines removed. The equivalent of taking those two squares and removing the border between them, so you would have just one rectangle.
As it was presented in the OP, I don’t think it is a shape. If I get two squares and stick them next to each other so one side of each is touching, have I suddenly got one rectangle? Or do I still have two squares with a border between them?
Someone else posted an amended version with the internal lines removed. The equivalent of taking those two squares and removing the border between them, so you would have just one rectangle.