I hadn't, until I came across this video clip of 'freeborders' zooming down mountain passes near Bormio in northern Italy. Wikipedia defines a 'freebord' as follows:
A freebord is a type of specialist skateboard designed to closely simulate the behavior of a snowboard. They have 6 wheels - two spring locked castor wheels on the central axis, and four slightly raised conventional wheels. The central wheels are able to turn freely in all directions, which allows the Freebord to slide laterally as long as no other wheel touches the ground. By exerting some pressure on the edge wheels, the Freeborder is able to control the board. The central wheels thus mimic the deck of the snowboard, while the outer wheels mimic the two steel edges.
They certainly look highly maneuverable! See for yourselves. (It's worth watching in full-screen mode.) LANGUAGE ALERT: Whoever selected the music (?) soundtrack for this video wasn't overly concerned with rude words. Personally, I wish they'd left the music out altogether!
I want to know how they manage to brake their 'freebords' if they go round a corner, only to find a truck coming the other way! (I presume these passes were closed while they filmed the video.)