The traveller is a rail on which a slide runs, with which the hoist point of the sail can be shifted from windward to leeward. This slide is adjusted by means of the traveller sheet on both sides, and is used to trim the mainsail. It is by adjusting the angle of attack of the sheet on the boom and thus affects the shape of the mainsail.It can be let pressure out of the mainsail (fieren) or also more pressure is generated (dicht holen) to drive a little more height in little wind. The sail can be made more bulbous and flatter. A traveler is not only interesting for regatta sailors because of these possibilities, but also for cruising sailors a safety relevant accessory, because it simplifies the control of the boat considerably. On some boats there are also headsail travellers which ensure that the headsail can be easily tacked when using so-called self-tacking jibs.The most common manufacturers are: Harken, Sprenger, Pfeiffer and Lewmar.Traveller tracks and slides, if attached to the trailing edge of the mast, are also used as so-called battened traveller systems on battened mainsails to recover the mainsail. Modern travellers are almost always ball bearing mounted.