Answer:
My sides are firmly laced about, Yet nothing is within; You'll think my head is strange indeed, Being nothing else but skin.
It cannot be seen, it weighs nothing, but when put into a barrel, it makes it lighter.
What can't you see, hear or feel, until its too late. What shadows love, and shopkeepers hate?
Take one out and scratch my head I am now black but once was red.
The person who makes it has no need for it. The person who purchases it does not use it. The person who does use it does not know he or she is. What is it?
I have two eyes in the front and a lot of eyes on my tail