Shoes are a key to leaving the house

We have to crate our dog Molly when we leave the house because she will destroy everything in sight!!!  We have her a nice crate with a soft blanket and pillow. All we have to say is:  Molly we  have to go and she will go to her crate and lay down.  This morning she was watching me get ready to go to work.  I sat down on the bench by our bed to put on my shoes and she was on the our bed.  As soon as she saw me put on my shoes she jumped down and got in her crate and waited for me to lock the door.  I didnt have to tell her anything.  Smart dog!!!!