be part of the furniture

So imagine you've been working in the same office for a very long time. You are there almost everyday, and leaves at night only to go to sleep and return first thing in the morning. You feel like that office is so part of you that you've become part of the furniture.

When you're part of the furniture of some place, it means you've been there for so long you've become a natural part of it. Many teenagers spend much time of their days in front of their computer and stuck in a room. When their moms call them out, they may say they seem like part of the furniture, because they never leave that room. And that's the expression of today. Take care!