Pillars are, like the mainplate and the bridges, part of the movement’s cage, not to be confused with the tourbillon cage.
Pillars replace the body of the bridges and make the link between two plates, one is the mainplate and the other is what we could call the upper part of the bridge. These pillars were mainly present on the movements of the Paris clocks and on the marine chronometers.
In the history of watchmaking, they have always been machined in brass and more precisely in brass of a slightly greenish color. This is due to the fact that at the time of the manufacture of these objects, the brass was free of lead, which was later added to facilitate the breaking of the chip during the machining process.
Pillars are still manufactured on a few rare examples whose manufacture is inspired by old marine chronometers.