note: silencers are most likely prohibited in your area without a special license. Check your local laws before attempting this. Also, this instructable is purely for informational purposes and could be dangerous and prohibited.
Step 1: Locate Your Materials
In a post apocalyptic world, you are shopping in a supermarket with your high-powered sniper rifle slung across your shoulder. All of the sudden, alien invaders burst into the supermarket. You notice that the head honcho alien who's brain serves as a central brainwave server is among the intruders.
Seeing as how the aliens havn't seen you yet, you quickly devise a plan.
You grab the items from your cart and jump on top of the freezer isle behind the igloo coolers.
Your plan is to take out the honcho alien without revealing your position. Since your not super creative, you don't think of anything clever aside from shooting him. So! you need a silencer.
Among your grocery items you happen to have a newspaper, a 2 litre bottle of soda, and some electrical tape. Good! thats all you'll need... plus your trusty sniper rifle.
Step 2: Prep Your Materials
Then you wrap the barrel of your rifle with electrical tape until the mouth of the bottle will fit snugly onto the barrel. You secure the silencer onto the barrel with some more electrical tape and peer from your perch in order to locate the aliens positions.
Step 3: Take the Shot Then Admire Your Work
As you exhale your finger eases onto the trigger. A muffled "pop" sound eminates from your barrel. BUT because your silencer screwed up the trajectory of the bullet, it misses the target. It ricochets off the hardheaded store manager and strikes the alien anyhow.
Mission Accomplished. The other aliens flee the scene, the town, earth in it's entirety, and you can sit back and enjoy a brewsky.
Once again, I must warn you. This really isn't a good idea to do in real life due to it's danger and legality, but it's good info to know for a post apocalyptic world.