This instructable will tell you how to make a bottle cap catcher in 5 minutes. All you will need:
-Wall mounted bottle opener
-About 10 paperclips (give or take for drop distance)
-An 8.5x11 inch piece of paper (or a square piece to skip a step)
-Binder clips x2 (or a paper hole punch (not the 3 hole punch, unless you're clever))
-Optional, but recommended: A beverage with a non-twist off cap (beta testing)

Step 1: Mount the Bottle Opener

Mount your bottle opener wherever you please, as long as you're not breaking any rental agreement on putting holes in your wall. Most bottle openers provide instructions.

Step 2: Paperclip Chain.

Chain together about 10 paperclips. Give or take a few for distance adjustments from the bottle opener to the catcher.

Step 3: Paper Box (well Half a Box)

Fold an origami box. I followed this instructable:

https://www.instructables.com/id/Classic-Origami-Box

When you're done, either attach the binder clips on either side like I did, or punch a hole in lieu of the clips. (the holes may work better on the far sides (away from the wall) of the box since there is no weight addition with holes). If you want, you can remove the clip sides on the interior of the box. I did it to make the final presentation a little cleaner looking.

Step 4: Assemble the Components.

String the paperclip chain through the space between the bottle opener and the wall. (this may take a little finess).

Attach the paperclip chain ends to the binder clip 'handles' on either side (or the holes if you choose that option).

Adjust the binder clips position to get the best hanging position.