From the publisher:
Battlegraph boards allow the game to have a scrolling battle map right in the center of your table. As the action progresses across the high quality dry erase surface, explored areas can be removed, erased, and placed toward the front where the map can continue on. Because the boards are interlocking the map is easily placed back to the center of the table where the battle rages on!
The grid lines are permanently etched into the crisp white surface which makes drawing straight lines a breeze, because the marker tip falls into the groove and follows it as if you were using a ruler. This speeds up prep time considerably. The white surface allows for the use of any color of dry erase you can find, and makes for amazingly vivid maps.
Want to take your time and draw out a masterpiece for that final climatic encounter? No problem! And you don’t have to waste valuable game time to do it. Just draw out the scene in vivid detail ahead of time and then stack the tiles together using small pieces of non slip drawer liner material available for cheap at any grocery store. The rubbery material will provide space between boards to protect your work of art, and since it is non slip, it keeps the stack from sliding around and erasing your masterpiece.
This same technique can also be used to create fog of war effects since only the boards that the players are exposed to need be placed on the table.