Answer:
They have not flesh, nor feathers, nor scales, nor bone. Yet they have fingers and thumbs of their own.
Where do you go in through one hole and come out through two holes at the same time?
Through its wounds, water does run. It once held many but now has none. What is it?
In buckles or lace, they help set the pace. The farther you go, the thinner they grow.
I run through hills. I veer around mountains. I leap over rivers. And crawl through the forests. Step out your door to find me.
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?