So...you have a pair of sunglasses...or two....brace style or otherwise...and the screw fell out and you don't have another set...no problem!
Take some armiiture wire....20 guage copper, or otherwise. (I've also done this with flux wire and soldered it afterward) here's what you do...make a wirework design on one end of 3 inch length of wire...using a pair of pliers...been the wire back leaving the end strait. Place the wire thru the opening in the frame and lens (brace style) of the glasses from the front so the decorative knot shows...make a lock knot with the wire on the back tightening as needed. If the brace frames has two holes. You can bring both ends thru from the back and make a double decorative knot on the front tightening as you go. Also you can make a wire knot and insert from the back and make a decorative closure.
If you're just reconnecting...make the knot wire...trim the wire down to 1 inch, bend back flush with opening after inserting the wire thru all rings of the frame connector. Wind a knot as close as possible to base...press with plirs. Done.