Who greases the books?

I would have loved to have written that in Latin, but sadly a classical education eluded me. One of the sites/sights that Amy and James showed us was the magnificent Giles Gilbert Scott University Library. I absolutely loved this building, possibly even more than my own, contemporaneous but in some ways very different, one.

Outside is an example of the now-ubiquitous public art to be found in all new developments (the building itself dates from 1934, but there have been many subsequent extensions). Called Ex Libris, it is a row of columns of stacks of books, cast in bronze. Some are solid, but in some of the stacks, the books can all be rotated individually, leading to hours of fun as the more anarchic spin them randomly, and the tidy-minded come and straighten them up again.

Amy demonstrates...

But I wonder how many people go round them looking for the grease nipple? Oh, just me then. Because (pointless as they may be) they are so beautifully engineered, and rotate so smoothly, they must be being greased somehow. Ah well, ars est celare artem.