Hoofddorp is a special case in the Position Amsterdam. It is equipped with an unique armoured caponier armed with four machine-guns and three rifles. The fort is located in a polder SW of Amsterdam. The main defense line runs straight through the polder. However to prevent that the entire polder would be inundated a dike was built here. This kept the friendly side of the polder dry and enable the defender to move men and material outside the view of the enemy.

However the dike also gave some problems. It was laid outside the village Hoofddorp where the dike makes a sharp turn. At this point the fort Hoofddorp was built to defend both the dike and a nearby waterway with an inundation sluice. However in order to be able to fire over the dike Fort Hoofddorp was quite high. But this made an effective defense of the ditch from the remparts of the fort impossible. Therefore an armoured caponier was needed.