What do the two bedroom bell-pull switches in the Boyles' mansion do?

dishonored

It opens a hidden hatch above the shelves, giving access to a secret area.

Related

Can I save my campaign on computer 1, and then continue on computer 2?
Archangel's or Manamune on Ryze?
Any way to play an "original" game of Civ 5
Is it normal for a dragon's body to disappear and for it to keep attacking the same place again?
Skyrim character freezing repeatedly
Weapons upgraded automatically
How can I mitigate disease?
Are there any repercussions to killing Policemen? [duplicate]
I'm sucking in the early game -- what missions should I undertake?
How do you defeat the revenants in the Brecilian Forest?
What should I look for in a Hunting Horn?
How do you exit the console in Battlefield 4?