At Asperen there is a special lock complex in the river Linge that was of crucial importance for the New Dutch Waterline. In the event of a threat of war, the two inlet or 'inundation locks' in the two Linge dikes could carry the water supplied via that river to the surrounding polder area and flood it (inundation). In that case, the two weir locks in the river were closed, so that the water was pushed up high to the east of the Diefdijk Line. The closure was done with so-called bulkhead beams, which formed a sheet pile wall on top of each other. Next to these locks are still the old storage places for these beams.
The double inundation locks or fan locks, the doors of which together form a kind of fan, are special because they can even turn against high water and can also be closed in running water. Yet only one man is needed to operate the huge colossus. When the locks are closed for a long period of time, a double row of stacked bulkhead beams in each lock acts as a sheet pile wall.
In times of peace, the usually closed and now beautifully restored fan sluices came and do come in handy in the opposite sense: in the event of flooding, the bulkhead beams come out and drain excess water to the Linge.
The weir locks are located just southeast of Asperen at the spot where the Meerdijk changes into the Nieuwe Zuiderlingedijk. These dikes are part of the Diefdijk Line that marks the border between South Holland and Gelderland. The polders to the east of this 23-kilometre long line would disappear under water in the event of a threat of war in order to stop the enemy. Where the Linge intersected the line, a dam was constructed in the river, with first one and later two weir locks. These had to close the opening in the line in case of emergency.
The inundation sluices are located a little further south on both sides of the river, in the Zuider- and Noorderlingedijk. Two forts were built to protect these important military waterworks: Fort Asperen near the eastern one and the Wapenplaats near the western lock.
In the vicinity there are several concrete group shelters from different periods, along the Meerdijk there are battery shelters from 1905. There are also remains of a single machine gun casemate, intended for extra defense of the lock complex.
The two fan locks were built in 1815, at the start of the first construction period of the New Dutch Waterline. The innovative design was by hydraulic engineer Jan Blanken. In the same year, three more examples were constructed within the New Dutch Waterline, at Werk aan het Spoel, Werk aan de Bakkerskil and Vesting Woudrichem.
Improvements were made to the locks in 1882. In any case, repair was regularly necessary, because of the destructive effect of the water on the originally wooden lock gates.
Flooding large areas of land could take up to four or five weeks. With the rapidly advancing weapon technology, that would not suffice for long. That is why later in the nineteenth century inundation canals were dug here and there. One of them ran from Tiel to Wadenoijen. This canal accelerated the flow of water from the Waal via the Linge and the sluices at Asperen to the polders east of the Diefdijk Line.
In April 1940, when the Germans attacked Denmark and Norway, the locks at Fort Asperen were opened. However, the water line turned out to be obsolete due to the use of aircraft and paratroopers. At the end of the war, it was the Germans who opened the lock again in the hope of a safe retreat.