I started with two identical plastic soda bottles to make sure that they would match in size. I cut the necks of the bottles off using a small hacksaw making sure that I kept the large flange that would be used to glue the two necks together later.
Step 1: Cut Off the Necks
Once I had cut off the neck of each bottle I used a flat file to smooth down the rough saw marks and left over plastic. The idea is to remove all the rough edges until you have a flat surface level with the large flange as this will be where you will glue the two pieces together.
Step 2: Smooth the Edges to Be Glued
Here are the two sections of bottle necks ready to be glued together. I made sure that they were both clean and free from any rough edges that would stop good contact.
Step 3: Glue Pieces Together
The final result is a small water-tight container with two ends that can be open via the lids. The total weight of the container is 0.5oz and it took about 10 minutes to make including the time to let the glue set.
Step 4: The Finished Result
If you have some time and a few spare plastic soda bottles laying around, give it a try. After making this one I made another one with an additional flat piece of plastic sandwiched between the two necks that created a dual compartment container. I think I'll use it for salt and pepper!
This instructable was originally posted on Brian's Backpacking Blog.