# ownership and borrowing
I'm always confused about which valuable has `ownership` or `borrowing`.
The following code was good example to understand the relationship of `ownership` and `borrowing`.
impl Drop for ThreadPool {
fn drop(&mut self) {
for worker in &mut self.workers { // 1.
println!("Shutting down worker {}", worker.id);
worker.thread.join().unwrap();// 2.
}
}
}
This will occur the following error.
```
53 | worker.thread.join().unwrap();
| ^^^^^^^^^^^^^ ------ `worker.thread` moved due to this method call
| |
| move occurs because `worker.thread` has type `JoinHandle<()>`, which does not implement the `Copy` trait
```
This means that the point 1. shows we only borrows Worker instance's pointer.
But the point at 2. shows we try to take ownership to `join()`.
That's why the code won't compile.
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