Access via Detention Block, The Manufactory or Ring of Law
This structure is housed within a small room near the entrance to the instance. The lock controls a movable bridge, which connects the upper levels of the Ring of Law with The Manufactory. This bridge is the only way into The Manufactory, and thus the only way to reach the back areas of the instance.
The lock can only be activated with the Shadowforged Key, which can be obtained with the completion of the quest Dark Iron Legacy.
The lock can not be picked, opened with a skeleton key or demolished with seaforium charges.
You can avoid fighting the mobs, if you send a druid or a rogue to open the lock, who can do this undetected.