Captions are short texts accompanying other objects, like statues, buildings, rooms, mirrors, doors, and paintings. The can be written on the object with ink or paint, or they can be written on a piece of paper or parchment that is applied on or next to the object.
In the Geraardsbergen manuscript we find many examples: Text 25, Text 26, Text 30, Text 32, Text 35, Text 38 and Text 45, etcetera.