It may well be imagined that guilds so jealous of their prerogatives did not make it easy for merchants and workmen coming in from outside. In the free towns (i.e. towns in which industry was organised) a master's licence obtained in a neighbouring, or even a sister, town, was invalid, just as to-day the diploma of doctor of medicine gained in one country does not carry with it the right to practise in another. To open a shop, it was necessary to have served an apprenticeship in that city; or at the very least it was necessary to have learnt the trade for the same number of years demanded of the apprentices in that district. The merchants who came from other parts, not like birds of passage to disappear with the fairs, but to settle down and establish themselves in a country, were subject to the same dues as the citizens, but did not share with them the franchise and might not join their guilds. They formed colonies and attempted to obtain, or even bought permission to reside and trade; but they ran the risk of being arrested or turned out at any moment, especially if they were money-lenders, as, for instance, the Lombards, who both in France and England many a time suffered from these intermittent persecutions. Outsiders, even though in many cases they had originally come from the district, were hampered by all sorts of restraints and obligations. In short, the town market was usually reserved for the citizens of the town, and the policy of the guilds (with occasional exceptions on the part of the great commercial guilds) was to shut the door to all foreign goods which they could produce themselves. Even within the city walls it was their ambition to ruin, or to force into their ranks, free lances of the same trade;[48] and although the word "boycott" was not then invented, the thing itself already existed, and was practised when necessary. This tendency to preserve craft monopoly led to other practices, and we find each guild jealously guarding its particular province against all intruders. Doubtless in those days an article was as a rule wholly produced in a single workshop, but it sometimes happened that an article had to pass through the hands of more than one craft guild; this was the case with cloth, leather, and arms. Sometimes, again, a craft which began by being simple became so complex that its very development forced it to split up. Thus we find in some large towns that the wine merchants were subdivided into five classes: wholesale merchants; _hôteliers_ (hotel-keepers), who lodged and catered; _cabaretiers_ (inn-keepers), who served food and drink; _taverniers_ (publicans), who served drink only; and _marchands à pot_ (bottlers), who retailed wine to be taken away. It followed that the dividing line between guild and guild was often very doubtful, and this situation was continually giving rise to differences, quarrels, and lawsuits, some of which lasted for centuries.