A strategic object within the fortress was the Linschotersluis lock, with the adjacent Heulbrug from 1767. In 1367, the Linschotersluis was constructed within the city.
The bridge and lock were later rebuilt many times. The corresponding lock keeper's house is located at Vinkenbuurt 1. The Heulbrug from 1767 was part of the rampart that connected Lange Burchwal to Biezenwal. At the end of the Lange Burchwal stood the Linschoterpoort, right next to the Heulbrug. An image of this can be seen on the sign on the terrace next to the bridge.