Barricades and obstacles can be very usefull in 40k games, especially in cityfights. The easiest way to go is to take the GW plastic sprue, cut the barricades and put them on the table. Primed black and with a metal drybrush they look pretty decent. I took things a step further and mounted my barricades on bases, which makes measuring easier. According to the 40k rulebook (3rd ed) and most tournaments that require barricades use a size of 6" x 1". I split this in two to make the barricades more flexible and keep them legal rules wise at the same time.