If you're really in a pinch for some high quality caffeine, there are no coffee shops around and all you have is say, a hotel coffee maker in the bathroom (gross), this life hack just might perk up your day!
Bend the wire to be just a bit larger than the opening of your glass or mug. If your glass gets smaller at the bottom your wire may need to be bend with a smaller diameter or be made of a softer metal (coat hangers are quite stiff).
Make sure to clean off any lacquer or paint from your wire. A scotch bright scrubbing pad works well. Don't forget to clean up the length of the wire as well, past the point where the coffee level will be once the plunger is submerged in your glass or mug.
Squeeze the ring closed and use the hook we made earlier to grab onto the beginning. After that, bend the wire in such a way that the vertical portion is over the center of the ring rather than on the side. This will help the plunger go down the glass or mug evenly verses tipping to one side.
Check the size of the ring and ensure that it is just larger than the inside diameter of your glass or mug. Also adjust the ring to be as perfectly circular as you can to avoid spill over on the edges.
To avoid scratching up your mug (like I did) while testing, use a spare coffee filter or thin paper towel. Although a little baking soda, water and a scotch bright takes them right off.
Pour hot water into your glass or mug along with your coffee grounds and let it stand for about 4 minutes.
After the coffee has finished steeping, center the filter on top of your glass or mug. Place the ring over the filter and gently push the ring down into the coffee. To ensure a smooth start, you may need to push the edges down with your finger, sliding around the perimeter. Now plunge the filter slowly, all the way down.
If your edges don't seal you'll be left with grounds in your coffee (yuck!). But no worries, just grab another filter and adjust your ring then press again.
If you were able to get a good seal you should end up with a perfect cup of coffee (better than that hotel machine anyway).
To help get a seal, if you wire bending skills are not quite working out, try sliding a length of small diameter plastic tubing over the ring. Using this method your ring will need to be a bit smaller but the overall diameter including the tube should still be a bit larger than the opening of your glass or mug. The soft plastic of the tube makes getting the seal right the first time much easier.