The Lemstersluis is the lock complex that links the IJsselmeer to the Frisian inland waterways — for many sailors heading north into the lakes and canals it is the gateway. Two parallel chambers handle pleasure craft, with a separate sluice for the freight that still uses the route up to Heerenveen.
The locks open on a published timetable in summer and on demand the rest of the year. Standing on the central island while a chamber empties is the easy entertainment of a Lemmer afternoon — water boils, fenders squeak, and ten or twelve boats rise and fall together. A small lock-keeper's house carries an information board on how the system works.