Everything needed to build this Milk Bottle Saddle Bag is relatively cheap and common.
4 recycled one gallon milk bottles.
1 roll of Duct Tape.
1ft 8 inches of Velcro with adhesive on one side.
Paint/decorations of your choosing.
Step 1: Building the Saddle Bag
2. After cut all four milk bottles at the point just below where the bottom of the handle ends and is noted by the black line in photo three below.
Note. Before starting part 2 of this step two of these milk bottles should already have had their bases cut off, so the part that comes off after the cut is a top and middle section (photo 3). The two milk bottles that have not had their bases cut off now form a top and a middle + base section (photo 3 but the base would still be attached to the middle section).
At this point you should have 2 base sections, 2 middle sections, 2 middle + base sections, and 4 top sections.
Step 2: Putting the Lower Section Together With Duct Tape!
Next place the two next to each other and connect with Duct Tape as seen in the second below photo.
Then connect the bottoms as seen in the third photo.
It can be problematic, however, if you are trying to fit something of size into your saddle bag and there is a wall dividing it into half. A quick fix is needed and all you have to do is cut out the dividing wall with your Exacto knife and then cover over any sharp edges with Duct Tape. Just be sure not to cut through the bottom.
Lastly cover the rest with Duct Tape or something of your choice. I used Duct Tape because I felt it would help keep some of the water out and help the saddle bag weather a little better over time, along with the fact that it is holding everything together. I had two half rolls of Duct Tape which is why there are two different colors but if you have a better decorating idea go for it. Perhaps a reflector for cars, or decorations for the holidays, whatever seems most fitting to you.
Step 3: The Top
Step 4: WATER PROOFING SEAL!
There is a very simple and easy fix to this, though. Simply roll the Duct Tape around the bottom of the top with just about a half inch of the Duct Tape's width on the top and the rest hanging down. Then do the same on the inside so that the adhesive is touching the adhesive and resulting in a lip hanging down from the top.
Try putting the top onto the bottom. The seal should be quite tight and I found that if I picked up the entire saddle bag from the top the seal was tight enough that it help the bottom on without falling off.
Step 5: How Does It Stay on a Bike?
Take four, two inch longs strips of Velcro hooks and place two on the front and two on the back of the lower part as shown in the photo below.
Then take four, six inch long strips of Velcro loops and attack them to the top part of seen in the second photo but make sure there is some slack of them to open and close / hook onto a bike.
Voilà. You now have a saddle bag. Not only have you recycled but now possess one of the rare and coveted saddles bags made of milk bottles that will be the envy of all your friends.