Baby formula is often packaged in cardboard (like Pringles) or metal cans. The cardboard style has a lovely matte finish and the paper comes off easily. You can make this Instructable with either type of formula can.
Step 1: What You Need
7 empty 25.7 ounce formula cans;
Strip of 3/4" plywood, 5" x 36";
Awl or sharp nail;
Tape measure or ruler;
21 1/2" screws;
4 2" screws;
Sinkers or other mounting hardware appropriate for your home's walls
Step 2: Ready Your Cans
Peel the wrappers off the cans and wash them. If using the cardboard type, don't let them stay wet for too long. Turn the cans bottom-up and use the nail and hammer to make 3 starter holes in each one. I estimated the location, but if you are super-anal, make a template with the three holes equidistant from each other and about an inch from the can's edge.
Step 3: The Plywood Strip
Drill 4 holes in the plywood to mount the unit to your wall. They should be 1/2" from the edge and 1" from the top/bottom. Mark the unit's location on your wall with the level and put your sinkers in. (My walls are brick, so I can't give most of you any advice about finding your studs. I can tell you that the finished unit weighs about 4 lbs.) Don't hang the plywood yet.
Step 4: Mount Those Cans
Find the center of your plywood strip and mark it. Position a can in the center so that the triangle of your nail holes points downward. When it is centered horizontally as well as vertically, drill the screws through the can and into the plywood. Then, working from the center outward, attach the next 5 cans to the plywood strip. Position them so that the globs of glue aren't visible.
Step 5: Up on the Wall
Hang the unit to your wall. Then attach the last two edge cans and start storing!