The Kiesterzijl was named after the nearby hamlet of
Kie and was the largest and most important
lock () in the
Slachtedijk. The lock gates were usually open and were only closed in times of emergency, such as during a heavy storm when there was a risk that the
seawall could collapse and the Slachtedijk had to hold back the water as a
sleeper dike. Hence the names ('
control lock') or ('guarantee lock') for this lock. The dike then closed off the water from the Harlinger Zijlroede, called from 1645 and Van Harinxma Canal from 1939. It is assumed that the Kiesterzijl was constructed at the same time as the creation of the old Franeker-
Achlum polder, somewhere between 1000 and 1200. The name only appears for the first time in 1511 as
Keesterzyl and in 1543 as
Kiesterzyll,
Kisterdazyl and
Kyesterzyll. in 1664 it became
Kiesterzyl and from the 19th century
Kiesterzijl. It was originally a wooden lock, which was replaced by a stone one in 1698. In 1837 the lock was renewed again and three stream holes were added instead of one. There were two lock doors in each opening and a swing bridge was located above the middle flow hole. As part of the improvement of the
Fonejacht-
Harlingen waterway, the Kiesterzijl was located a little further south in the Van Harinxma Canal. The lock now had two passages that were no longer closed with doors, but with a series of long pipes that were lowered into
rabbets. The swing bridge on the center pier was equipped with grabs and the bridge functioned as a 'crane' that lifted the pipes from the embankment, raised them above the trenches and then lowered them. With this system it was not possible to close the passages in time during stormy weather. That is why in 1956 a complete hoisting system was installed on the north and south sides of the bridge, which made it possible to close the passages with the pipes within two hours. This installation was removed in 1996 because the importance of the Kiesterzijl as an emergency barrier was of little use anymore. ==Hamlet==