We just added the new Slumbershade blackout roller shades by Comfortex. This roller shade is an inside mount only application where you add tracks to the sides of your opening where the material runs up and down on. This eliminates and light seapage from the sides. The rails attached with magnet tape so installation is a breeze.
The top part of the roller shade is a fabric wrapped cassette. The top of the cassette prevent light from penetrating from the top. It also include a continuous corded bead chain that make raiseing and lowering of the shade very easy fro any angle.
This is the second total blackout material that Comfortex has come out with in the last few months and they are calling it the Slumbershade line. Both have been endorsed my the National Sleep Foundation as an excellent source to block out light. Having the rails actually does more than just block out the light. it also reduces sound and makes the shade extremely energy efficient.