This printed brick card is great for lining the first 6-8 inches of the entrance/exit of your tunnels. It is a very nice slightly embossed card stock that bends or rolls very nicely to slip inside a tunnel entrance. I was able to cut the 26 inch long card into 4 equal pieces 6 plus inches which is plenty since you can not see any farther than that inside a small HO tunnel. And any further back into the tunnel than that is generally pained flat black anyway. I first coated the inside of the tunnel walls that would come in contact with the card stock with Mod Podge matte glue, then rolled the card stock gently not creasing it and slid it into the tunnel and let it spring open and adhere to the inside of the walls. Be sure to position it where you want it before drying. Another tip is this.. if you have a tunnel that you can only see one side of the interior of the tunnel wall. An example of this would be a tunnel entrance is up against the layout backdrop or hidden by a mountain where the backside can't be seen. In that case only line the tunnel wall that can be seen by an observer walking around the layout. This way you don't waist material unnecessarily decorating hidden areas of the layout.