Its actually called a pelmet board and can be any size you like. If you visit the DIY Projects section and look at the project on curtain poles or adhesives used at home you will see how one can be fixed. There is also a project about drilling into steel lintels where it is suggested a pelmet is glued to the wall above the window using a construction adhesive.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!