trim or clean the rough edges

pas le sens d'ébavurage ici

"Fettle, fettling:
Making repairs to rail track, especially concerned with maintaining the drainage of the ballast, and the proper cant of the rail track and rails."
http://www.translationdirectory.com/glossaries/glossary256.p...

"Dipped joint - a dip between two rails in jointed track caused when voids have formed in the ballast under the joint sleepers.
Fettle/fettling - removal of said voids by the P-way gangs using voids using bars or ballast forks. "
http://districtdavesforum.co.uk/thread/810/railway-slang?pag...

"In the railroad industry, this term is used to describe routine maintenance performed on tracks. It includes confirming that the rails are aligned properly, checking drainage systems, replacing ties if necessary, and conducting other tasks which will keep the tracks in good condition. It is important for this maintenance to be performed on a regular basis since a wide variety of situations can cause damage to the tracks, and this can result in damage to trains passing over the tracks, most spectacularly in the case of a derailment.

Track fettling is usually accomplished with the assistance of a small handcar or truck specially fitted to roll on the tracks, which allows track workers to carry tools and replacement parts as they traverse the track to inspect it. This is done in constant rotation to make sure that all of the track is seen at some point or another."
http://www.wisegeek.org/what-is-fettling.htm

"fettling the track bed
notice : no track laid yet!
http://www.geograph.org.uk/photo/3581446

video : track fettling
https://www.youtube.com/watch?v=34bywusqAEU