Simplify the following text for a Grade 7 native English-speaking person.
Original: Simon Monroe patented a hair straightener in 1906 that comprised 7 metallic teeth that are combed through the hair , while in 1909 Isaac K. Shero patented a hair straightener composed of two flat irons that are heated and pressed together .
Simplified: In 1909 , Issac K. Shero patented a hair straightener made of two irons that are heated and put together around the hair .