Thanks, Jan! Great idea! I was about to warn ladies if they lived where I do that the mat might melt if left out too long. It's been Hot! We are getting relief and a little bit of moisture now, but summer is not over!
I have heard some will use a hot hair dryer on mats, but for severe problems it might not work.

Go to the olfa site there should be instructions there to flatten

When do you need to place mat in the bath? Would out of shape and water be any use ?

Jan, you always do the best pictures to make learning/understanding easy!

I don't understand the concept of putting your mat in the bath tub. My tubs aren't wide enough to sit the mat down flat. Do you just prop it up on the side and fill the tub?

You'll want to put your mat on a hot surface to flatten it. The hottest surface known to man is the roof of a car sitting in the New Mexico sunshine on a hot day :). You will probably have to flip it over a time or two but, once it is flexible get it off the car and lay it on a flat surface to cool.

I'm not sure what you mean by "plastic type". I might have to go have a look at Dollar Tree. Ordinary poster board might be okay indoors, though I'm not sure I see the point since it would flex as much as the mat. To keep them flat in a hot car you would need foam core, as Jan suggested. It stays rigid when hot and also would provide a little insulation. For a smaller mat, you might be able to find some free foam core after the next election when lots of people will have political signs to throw away. You could all your favorite candidate and offer to put a couple of signs in the yard, and then you won't have to scrounge for them after the election. But, of course, be honest and wait until it's over to use the signs for your intended purpose. LOL

Thanks for sharing this great idea, Jan! It's good to see you back here so soon. Hope it doesn't hurt to type!

I put mine on the hood of the car. This car had an old paint job, so wasn't worried about that, (not that it did anything to the paint js) I'm in Florida.