Answer:
A device for finding furniture in the dark.
Upon me you can tread, though softly under cover. And I will take you places, that you have yet to discover. I'm high, and I'm low, though flat in the middle. And though a joy to the children, adults think of me little.
Voiceless it cries,Voiceless it cries, Wingless flutters, Toothless bites, Mouthless mutters.
I am a box that holds keys without locks, yet they can unlock your soul.
What has a single eye but cannot see?
What do angels sing in the shower?