Although there are many different types of plastic mats, from exercise mats to floor protectors, they likely come packaged or are stored in the same way: rolled up tight. That can be problematic, because the edges then want to stay curled up instead of laying flat. Gravity will get the mat to behave, though.
Fight Curl With Curl
Unroll the mat, as flat as you can get it. Then, flip it over and reroll the mat. Creating this opposing new curl shape will in effect straighten the curled plastic. Keep it rolled up (longer for thicker/less for thinner plastic) with a rubber band and check it every so often until the previously upturned (curled) corners are laying flat as desired.
Gravity Will Win
If a reroll doesn't work, or it's too cumbersome to roll backwards, roll out the mat and flip it over so the curled edges are facing up. Weight down the edges with objects such as heavy books. Leave weights in place until the mat lays flat without resistance.
Effective Elsewhere, Too
Both these strategies are also effective in taking the curl out of the edges of a newly purchased carpet, scrolled paper and other items.
Marley Kennedy has been a freelance writer for six years. Her work has been published in the US, Chin, and Argentina for publications such as Radar, Time Out Beijing, El Nuevo Dia and Buenos Aires Herald. Kennedy graduated from New York University with a degree in psychology.