Chessex - Reversible Megamat 1inch Squares Blue-Green (34½ x 48) CHX 97465Although every crease is different, most can be coaxed out. One method is to lay the mat out flat and apply several books directly on the crease for a period of several hours or perhaps overnight. Another method is to use warm water poured over the spot to soften it and then knead out the crease. DO NOT iron your game mat or expose it to excessive heat, sunlight, or flame.