What is in this image? Describe it as if you were explaining it to someone from the 15th century.

This image depicts a man engaged in a winter sport, seated on a contraption quite unlike the sleighs or sledges you might know. He is dressed in special attire, including what appears to be a hardened hat and a mask to protect his face, which would be peculiar to your time. The man holds two sticks in his hands, which help him maneuver. The vehicle he is on is fitted with long and narrow blades allowing it to glide over the snow with great speed; these are akin to the runners of a sled but much slimmer and attached to a very different framework. In the background, there are trees that resemble pines and a fence running along a path, all covered in snow, typical to a wintry scene even in your time. Another peculiar sight is a flag planted in the snow, marking perhaps a boundary or finish line of some sort attached to this sportive pursuit.