When geocaching, the best caches are the ones you have to search for more than once. Here is a small guide in creating one and example of one of mine.
Step 1: Things You Need
A snail shell or similar, a tube (here an eppendorf tube), a caulking gun and adhesive (I used a flexible clear adhesive.), a screwdriver and a tong. Furthermore, a screw, a rubber spacer, a steel spacer and two plastic nuts are needed.
Step 2: Making an Anchor
Place the rubber spacer in the lid, and screw in the screw, then place the plastic nut and tighten the screw enough to squeeze the rubber spacer to create a rubber seal in the lid of the tube. Place the steel spacer between the two plastic nuts and tighten the second nut to hold it in place.
Step 3: Fill the Shell With the Adhesive
When you fill the shell make sure not to have any air in the adhesive and fill the shell as much as possible. Don't overfill it.
Step 4: Drop in the Anchor
While the adhesive is wet, drop in the anchor, make sure to twist it in, so the air gets pressed out and thereby strengthen the bond.
After the adhesive has dried, this geocache can be placed in a drilled hole in a post, a hole in a tree and pressed into the ground. Thereby making well camoflaged and not easily spotted.
I know, this was a short description of how to make one. This is my first instructable. :)