You are traveling, you find a nice poster or print and need a way to get it home uncrushed. If you can buy a poster tube, great. If not, you can make one with empty plastic water bottles.
Step 1: The Tool
Cut off the top, and/or bottom of the water bottle; I used the small file on my fingernail clipper. It was a bit noisy but worked well.
Use as many bottles as you need to make it the correct length. I needed three.
A bit of tape would have been nice to secure the middle bottle but it's not necessary.
Step 2: And Done
This survived a day of travel in my carry-on bag and kept the print from being crushed, specifically the ends of the print. Surprisingly sturdy.