An Amsterdammertje is the typical red-brown steel traffic bollard that is used to separate the sidewalk from the street in Amsterdam. Amsterdammertje means literally 'little one from Amsterdam' in Dutch. The bollards have the three Saint Andrew's Crosses from the coat of arms of Amsterdam.
In the 20th Century the Amsterdammetjes are being removed from sidewalks. New and used Amsterdammertjes are sold online by the city government of Amsterdam.
Read more about Amsterdammertje: History