These are the feet of tourists at the Charleston, South Carolina visitor's center. The tourists queue up to get information about tours around the city and its attractions. There are only three servers helping them book their tours. These are the feet of the tourists being served. Others, waiting to be served, are standing to the left of the brass pole.
If no servers were busy, an approaching tourist would be served at the first position nearest the pole. This is on the right of this picture, where four people in one party are discussing their vacation options. Further down the line, two people are talking to server number two, and further still (at the top left of this picture) a lone visitor is with server number three.
The first server position gets the most business and other servers are called in to fill positions two and three as the queue requires.
We can see the server frequency of use in the next picture. There is more floor scuffing and wear at position one, less at position two, and the smallest amount of wear at position three - a discrete frequency distribution of server use.