I just finished putting down Bruce pre-finished Bruce hardwood flooring. I do love it. I bought by mail a x-large doormat that said it was to protect your floors in high traffic areas. Now I look at the back and it is rubber but has little flat nubs on it. I know I need rubber so it won't slip but will those little bubs leave marks on my floor? I wouldn't get the ones with pointed nubs but I am nervous.

The add specifically showed it on a hard wood floor so I thought it would be alright....

Thanks for any input.