The location of Willem I lock is explained by the desire to place the IJ-end of the canal as close as possible to the Port of Amsterdam.

That same year, King William I asked Inspector General Jan Blanken for proposals that would enable ships to reach Alkmaar, and to pass it.

[6] Somewhat later, on 5 May 1820 the works to dig the actual canal, mainly by expanding the Buikslotervaart and Purmerender Vaart were tendered.

[12] On 13 December 1824 the frigate HNLMS Bellona entered Willem I Lock to commence the first trip on the completed Noordhollandsch Kanaal.

[14] In late April 1857 the new, and therefore not fully loaded, steam frigate HNLMS Wassenaar arrived before Willem I Lock.

The explanation that was given, was that at Willem I Lock the water level decreases while the ship went through, while at Purmerend it increases.

The Purmerend gates did not have to keep out the sea, and the lock itself bridged a difference of only 52 cm in summer.

[18] On 27 July 1856 the government appointed a commission to investigate how the Noordhollandsch Kanaal could be made completely suitable to the needs of commerce and navy.

One of the questions it had to answer, was how it could make the Noordhollandsch Kanaal suitable to service the largest type of commercial ship.

This would become Willem III Lock of 110 m long, 18.20 m wide and 7.33 m deep below Amsterdam Ordnance Datum.

However, in case that the already underway North Sea Canal project would fail, the Willem III Lock would already be prepared to become part of a much bigger Noordhollandsch Kanaal.

[21] The extensive damage also makes clear why the extra Willem III Lock was built.

Double locks are rather common to British canals, and are also found in North America.

Its locks had to serve a handful of big ocean-going ships a day, as well as a much larger amount of small boats that already used the waterways before they became part of the canal.

Another aspect of using the locks was that at high tide, it led to the infiltration of salt water in the polders.

In 1864, shortly before the rebuild, this was given as 65.41 m, together with a width of 15.56 m.[24] Still, the effective length of the lock was smaller than 65.41 m, because one pair of gates swung inside.

The area which was not bothered by gates opening to the inside was only 56.86 m long, see 1865 floor plan.

On the Waterland side the small lock had fan gates, which can be opened against the high water.

[23] This gave the opportunity to drain higher grounds just like a sluice can do, i.e. so lower lying beds get deepened by creating an extra strong current.