Among his most significant contributions to the evolution of modern skateboarding, Rodney Mullen adapted the ollie, first pioneered by Alan Gelfand on vert (where Gelfand would scoop off the back trucks to obtain more air off the wall, but without popping the tail of the skateboard in the process), to flatground. This ability to pop the board off of the ground and drag it upward into the air, gaining significant altitude and air time, allowed ollieing onto rails and obstacles and opened the door to more complex flip tricks and other flatground tricks. The invention of this trick alone, even apart from the numerous other tricks that he has invented and his design work, has ranked Mullen as one of the most important skateboarders of all time. In response to the praise that he has received for the flatground ollie, Mullen stated in August 2012: