Answer:
In buckles or lace, I help set the pace. The farther you go, the thinner I grow. What am I?
I am an English word with 3 consecutive double letters.
Four leaves I have.
I am the ultimate killing machine used not once but TWICE I can be made by humans.
I'm not a bird, but I can fly through the sky. I'm not a river, but I'm full of water. What am I?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.