A protection letter, also a protection letter, warrant or sauvegarde, used to be a document in which a certain group of people or institutions by a high authority like the king was freed from robbery or firefighting by, for example, soldiers. >
Thus, a monastery could be given a sauvegarde, but also to certain vulnerable groups of people, such as Jews or Gypsies. Often one had to pay a substantial sum for a protection letter.
Something similar was the guide letter, which had couriers or other traveling people.
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