>>Flexwat dose not stick to the anything so you need to find some way to attach it to the enclosure. I have heard of people useing duckt tape or some type of glue.
You can also use that foil tape tha Big Apple Herp sells. It transmits heat, so if you need to cover the heat tape a bit to make it stay in place it isn't a problem. You can also use tacks, provided you put them through the clear areas of the heat tape rather than the wires. Finally, my favoriate method for racks is to lay the heat tape down over the rack, then cover the entire floor with a thin sheet of metal, screwed to the rack. This prevents tubs from catching on the heat tape and the metal transmits the heat very well.