Many pre 2010 cruising Jeanneaus are fitted with cabin top main single sheet systems similar to below, which are normally out of reach of the helmsman.
The option to bring the mainsheet within easy reach by using a modified "Double German" system - has become almost standard on many of the latest Jeanneau's since around 2010.
The two separate ends of the mainsheet turn on blocks on the sidedeck near the main shrouds and then run along the sidedeck, before being fed back through an optional clutch to the genoa or spinnaker winches, allowing the helmsman to either trim or release the main sheet from the cockpit. Care must be taken in avoiding chafe, and trip hazards, so wise to inspect similar systems on yachts. The pictures below are of the German Mainsheet system fitted on a SO36i. (Courtesy of Ewald)
There is a more detailed hints and tips article the on system being retrofitted to a SO39i