07:23 Dec 18, 2011 

...if there might be a typo, and it ought to have been 'galets de roulement à bourrelets'? i.e. the 'roulement' (singular) describes what these 'galets' are for (rolling), rather than suggesting that they have 'roulements' in the sense of bearings.
Galet is always a bit tricky, as it can be several different things in EN depending on the exact size and shape. Here, I can't help wondering if they aren't simply little wheels for shifting the thing around?

05:57 Dec 18, 2011 

Maybe it's the roller, a travelling roler