What is a gable stone?
A gable stone is a motif of architectural sculpture with a mnemonic* function. It is a stone tablet set at a certain height in the facade of a house or building, elaborated with sculpture and an inscription: representing as such a sign which intent is address indication, admonition or notification. The gable stone developed in the second half of the 16th century mainly in the Dutch speaking regions from a much older medieval tradition to be met with all over Europe, concerning all sorts of characteristics, signs and figurines that served as address indications to houses and buildings. Street numbering was only introduced in the Netherlands around 1875.
*Mnemonic: method to associate notions by the aid of various devices in order to support the memory.
Interesting websites (with images) about Dutch gable stones:
Amsterdam Gable-stones Society
Flickr images of gable stones
Hans ‘t Mannetje makes gable stones
More gable stones, also international
Wikipedia-information on ‘Gable stones’