If there is one thing I hate (there are many actually), it's clutter and a messy shop. That is two things ... nevermind.
I predominately use 3 grits of sandpaper with my orbital sander. 80, something else, and something else. I was tired of them sitting on a table only to fall off, or trying to use the packaging as some kind of clever tray when it wasn't.
I decided to make a caddy, which I could hang on my storage wall with a French cleat.
Step 1: Plywood and Then Some Holes
Grab some plywood. Mine was scrap 3/4" plywood, which ripped to 5 1/8" x 16". Mine holds 3 rows of discs. If you want more, make the board longer, or wider and do two rows.
Draw a center line lengthwise. Use that to line up your discs and trace three holes each. You could go more, but I see no reason. Three looks like a face and who doesn't like that?
3/8" dowel rod fits the holes prefectly, therefore I drilled my holes with a 3/8" forstner bit. I went 1/2" deep, but you can do whatever you want.
Step 2: I Painted the Board
I decided I wanted this board black, but not the pegs, so I painted it at this step. If you want to assemble it all first and then finish it, that is a good idea as well.
My pegs are 2 1/2" long so I can get a full pack of each grit on here. Also, I hand chamfered the edge of the dowel (with sandpaper ironically) so the paper would slide on easier.
Step 3: Glue in the Pegs
Little bit of glue in each hole and a few light taps with a mallet = done.
I gave it a few coats of spray lacquer for protection.
Step 4: Hang It and Use It
I initially had this screwed directly to the wall, but added a French cleat once I went that direction for shop storage. That works out well because I can move it around or even take it to my work table. Also, I went vertical to work better in my space, but horizontal could be cool as well.
The added bonus is the three pegs can function as a self-alignment jig to get the paper perfectly lined up on the pad and with the dust collection holes. Of you can just take a disc off the wall and put it on by hand, but you know it won't be perfect and you'll try a few times.