We sell HyperVent® by the linear foot. Place your order based on the number of feet you need. It's 39 inches wide. See Below for measuring tips.
Use a scissors or knife to trim a sheet of HyperVent® to fit your application. Then install HyperVent® with the loop side down and the cloth side up. Its woven polymer will not scratch standard surfaces.
HyperVent®'s manufacturing process is the secret to its effectiveness. The stiff matrix is 95% open, allowing air to freely circulate throughout the material while supporting the weight above. The mat is lightweight and flexible yet rigid enough to hold its shape indefinitely.
HyperVent® reduces dampness and the dangers associated with too much moisture such as mold and mildew. It accomplishes this is two ways: 1) it improves the sleeping surface by providing space underneath the mattress for warm air to circulate, 2) the circulating air promotes evaporation.
If your mattress is 39 inches or so in width (below left) apply the hyperVent lengthwise in one sheet. If your mattress is wider than 39 inches apply the hyperVent in sections crosswise (below right) and then add the sections together to estimate how much you need.
I installed the HyperVent material under the foam mattress on my 33' power boat to control condensation. The HyperVent did the trick.
We used HyperVent this year under the V berth on our 28' lobster cruising boat with great success. It allowed air to circulate under the cushions eliminating any moisture that might have been looking for a home.
Two layers in the bottom of the refrigerator keeps foods and beverages above any water accumulation. Lining settee storage lockers solved a mold growth problem by eliminating condensation on the hull.
My experience with this system is so much better than with other products I've tried. I can enthusiastically recommend HyperVent.