The Lockless Door

It went many years,
But at last came a knock,
And I thought of the door
With no lock to lock.
I blew out the light,
I tip-toed the floor,
And raised both hands
In prayer to the door.
But the knock came again
My window was wide;
I climbed on the sill
And descended outside.
Back over the sill
I bade a 'Come in'
To whoever the knock
At the door may have been.
So at a knock
I emptied my cage
To hide in the world
And alter with age.