It's included with products designed to use it. For more info, search the for "Masterboard".

I may be wrong, but I believe the "Chunky Dungeons" products are the only ones that use "Pro Masterboard"

"Pro Masterboard" is basically a playmat (a large piece of foamcore) on which you layout a square grid. You glue a piece of Velcro to each Masterboard square and the terrain pieces.

The "Masterboard" is an older concept we toyed with a few years ago. Its a fancy way of saying; one giant sheet of foamcore with a bunch of tiles glued to it Its a good way to go if you want to strictly define a playing area.

The "Pro Masterboard" uses a single sheet of foamcore with a grid of velcro squares on it. You then place modular sections onto this board to attach them in place. Chunky Dungeons (released 2004) was the only product to utilize this method.

TerrainlinX (launched this year) is obviously a much newer, hypermodular and generally much more flexible system. It basically addresses all the issues we had in the past while keeping layouts completely fluid. That said, we are still filling out our catalog with TerrainlinX products so older offerings are still your best bet for certain environments.