The way I did this included sewing. You can just use safety pins instead though.
And please don't use this to bring items to school (or another place) which shouldn't be there.
Anyways, you don't really need this for smuggling in items. I know people who bring large switchblades to school every day. With the giant hook hooked on the outside of their pants in plain view.
Step 1: Supplies
1. Thread that is the color of the inside of your backpack
2. Pins to hold the cloth up while you attach it.
3. Cloth that is the color of the inside of your backpack.
4. Duct tape the color of your backpack.
6. A backpack with a cd player pocket.
(7. If you don't want to sew, you can use safety pins.)
Step 2: Measure and Attach the Piece of Cloth.
Next, put the piece of cloth behind the cd player pocket and pin the four corners up. Watch out for when the needles come through the backpack and into the pocket.
Step 3: Sew the Cloth On
You will probably have to flip the backpack around to sew it, so just remember which way is going to be up.
Also, you will stab yourself at least once doing this. If you are amazing enough not to, I congratulate you. I'm just proud that I never saw blood from any of my wounds.
Step 4: Duct Tape Over the Edges
I had to rip each piece in half lengthwise so you couldn't see it.
Step 5: You're Done!
Also, if you have a backpack without a cd player pocket, there is another way of doing this.
Feel around your backpack for a double layered spot. There is usually one on the back, but that's not the best place for it. But if you have to, use it.
Just cut a hole in one of the layers, make the same pocket inside of it, and there you go.