The Workshop Entrance (sometimes known as the "Backdoor") of Gnomeregan is a subzone at the far side of the Workshop room just past the Train Depot in the non-instanced part of Gnomeregan. There is a door that once required the [Workshop Key] to open it and be able to access the instance through this area. Once in the dungeon, a hall will lead you to the Engineering Labs section of instance.
When facing the Workshop Entrance from the far side of the Workshop, the Loading Room opening is to your left.
Patch changes[]
Patch 4.0.3a (2010-11-23): Subzone added to an already existing area.