The henchmen of the wicked aren't just about collecting body parts, capturing damsels and lurking about, you know. They enjoy their downtime, as well. As you can see, skating is popular in the sub-chambers of the dungeons/laboratories. The surface, however, is not great (usually slick cobble stones) and the skates are, generally, those metal, adjustable kind. You know, the kind that makes the grinding noise, with the single cruddy, leather straps.
Henchmen don't mind, though. The feeling of the wind passing through their burlap tunic is a delight. The rats seem to like it, too.