What is it used for?

Screw Eyes are used to attach wire to the back of your frame so that you can hang the frame on the wall.

How do I use the screw eyes?

Much as the name suggests, you screw the eye into the back of the frame.  Then you weave the zerlon wire through the eyelets.

When should I use the screw eyes instead of the mirror hangers?

Screw eyes are meant to hold small, lightweight frames.  If your frame holds an image larger than 8x10 or a storyboard larger than a 3op 4x5, please use mirror hangers instead.  The weight of a frame (especially if it holds glass) can be too much for a screw eye and will pull away and fall off the wall.

If you are in doubt, use the mirror hangers.