Many times I have felt the need to use a magniloupe, magnifying glass whatever you want to call it. Some times it was to work on the innards of a wrist watch or some tiny gadget, but mostly I need it to extract a splinter from under my skin or some one else's. It's awkward holding a magnifying glass while trying to dig for that splinter with a sewing needle, especially if it's your own hand that has the splinter.
I found this method for affixing the magniloupe to my reading glasses very helpful.
FYI, in case you don't have a magniloupe, you can get one at an electronic store. Thats where I got mine.

Step 1: Parts Required

1. Reading glasses or just non-prescription glasses. Bi-focals won't work very well. You can get a pair of reading or non-prescrition glasses at most dollar stores.
2. Magni Loupe
3. Rubber band

Step 2: Place Magni Loupe in Position

The box is just to support the glasses while I took a picture. The Magni Loupe will attach to the outside of the glasses with the bigger side of the Loupe in contact with the glasses. I attach tio my right eye, but you may want to use your left. Whatever works best.

Step 3: Place Rubber Band in Position

As you can see, the rubber band goes from the other side (the inside) of your glasses.

Step 4: Twist and Slip

Final step.
Holding the loupe and glasses together, bring the rubber band around the loupe as seen in the picture. Sorry if it's not too clear. Each side of the band slips over and to the opposite side of the loupe, thereby holding the loupe in place.