The easy part is to describe this as a lock on the river by the lock keepers cottage.  It is about half way between Hertford and Ware in Hertfordshire. The hard part is what to call the waterway. The River Lee and the River Lea are both acceptable but is it infact the river or the Lee Navigation (Lea Navigation). Long ago part of the river was diverted in order to allow narrow boats (narrow barges) to, well navigate, towards London (about 26 miles away as the crow flies). In other words part of the river is actually canal. Narrow boats still ply the river (canal) passing through the locks, but now they are pleasure houseboats not goods for the capital.