The workman is gone. Now What?

Hint 1 of 11:

Did you examine the fireplace very carefully?

Hint 2 of 11:

Did you notice the hole?

Hint 3 of 11:

Too bad you don't have something that would fit into the hole.

Hint 4 of 11:

Did you notice that the workman left his toolbox behind?

Hint 5 of 11:

Is there something inside that you might find useful?

Hint 6 of 11:

Take the screwdriver.

Hint 7 of 11:

Use the screwdriver on the hole.

Hint 8 of 11:

Did you hear that click?

Hint 9 of 11:

Maybe you should investigate!

Hint 10 of 11:

The click came from the closet.