a snowboarder wearing a green hat is riding along a metal railing.
A snowboarder is riding along a metal railing while wearing a green hat.
While wearing a green hat is a rephrasing of wearing a green hat.
'A snowboarder is riding along a metal railing while wearing a green hat' is a rephrasing of 'a snowboarded wearing a green hat is riding along a metal railing'.
"A snowboarder is riding along a metal railing while wearing a green hat" is rephrased from "A snowboarder wearing a green hat is riding along a metal railing".