How to Make Spy Gadgets Out of Household Items for Kids

Find an old, hardcover book that you are no longer interested in reading or one that's ready for recycling. The thicker and larger the book, the more items you can be store inside it.

Open the book and turn the pages until you are approximately a fourth of the way through the pages.

Draw a rectangle on the right hand page using a marker or pen, but do not get too close to the book's binding as cutting into the book's binding will cause it to fall apart.

Have an adult cut along each line carefully using a utility knife. To avoid leaving ragged edges, cut only a few pages with each knife stroke. You can cut a space all the way to the back cover, or cut fewer pages for a more shallow space.

Place whatever items you want to hide into your new book safe and store it on a bookshelf. This is called hiding in plain sight.

Cut a two-inch square out of the end of a cardboard mailing tube, like those used to roll and send posters.

Cut two-inch diagonal slits at each corner of the square and flip the tube around, repeating the square cuts and the diagonal slits at this end but on the opposite side.

Glue mirrors to the squares along the periscope and inside each slit, with the latter mirrors facing the bottom. Add another small mirror to the bottom cut and use duct tape or dark opaque masking tape to seal up the ends of the tube to prevent light from entering.

Look through one end of the tube and it'll reflect images like a periscope.

Cut a lemon from the refrigerator or pantry into wedges and squeeze the juice into a glass.

Write out your secret message on recycled paper using the lemon juice and a make-up applicator brush and allow it to dry completely.

Deliver your secret message and have the recipient hold it up near a heat source. If you hold it near a source with a flame, be careful not to let the paper touch it or it will burn.