What are hygienic levelers?

I was surfin' the web and found these - hygienic levers. What are 'hygienic levelers'? My first thought was that they were like WoW players that actually bathed more than once a week before playing the game but that's not it at all.

A hygienic leveler is the thing that makes certain machines level with the ground. The machines that it levels tend to be food service items and medical equipment. Hence the hygienic part. The more you know...