“not straight”

“I bought this because it was wide enough to cut a non-slip pad for our handtied Turkish Carpet runner. I wanted it to come just to the carpet edge. I cut the exact dimensions along the grid lines of the pad. However, because of the way the pad had been folded and packaged, those grid lines do not run straight with the carpet and the pad curves out beyond the carpet on one side. I'm hoping it will eventually straighten out from lying flat! I don't want to cut it narrower because then it will form a little ridge under the runner (a place for wear).”