zipper slid

The zipper slid down of its own accord,
or gravity's, I guess
but - either way
that's a finely-tuned
machine! And I'm glad that it's on,
and that it's scored with best steel
finely-scaled rows of teeth. Because
I heard the zoom-rattling down

and I said:

This zipper holds its worth
in the easy and gliding descent

I've found