A standard pair of rimless prescription eyeglasses consists of two lenses, connected by a nose bridge and each with an ear bar extending perpendicular to each lens. With the correct tools, you can repair many problems associated with a pair of rimless eyeglasses.
Connect the nose bridge. In the event that the nose bar has come off on one or both sides, use two screws (or four, depending on the eyeglass model) from the repair kit to affix the nose piece to the lens. Each lens will have the holes drilled, so simply align the hole of the bar to the lens and screw from the outer lens in, using a small washer on either side of the lens and working the screw into the lug nut on the back. Tighten the lug nut. Depending on the frame and lens, you may have to ensure that you are connecting the lenses right-side up.
Connect the ear pieces. For disconnected ear pieces, align the hole of the lens to that of the ear piece, ensuring the curvature of the ear-cradle bar is positioned correctly and in accordance with how the nose bridge is positioned. Using a washer on either side, drive a screw from the outside in, affixing it to the small lug nut on the back.
Adjust the nose pads, temples and ear bars. Depending on the model, you may have a solid nose piece, or adjustable nose pads. Taking care not to apply too much pressure, use the needle nose pliers to slightly adjust the nose pads to a point that rests upon the bridge of your nose and does not slip down or pinch. The temples are where the ear bars meet the lens, and on metal frames can be adjusted. Use the needle nose pliers on this one, taking great care as well to adjust the ear bars so they aim comfortably to rest on your ears. Finally, adjust the ear bars gingerly with the pliers so the ear cradles rest comfortably on your ears and cause your frames to sit evenly on top of the bridge of your nose.