We've all done it. Used a carving knife to slice the lid of the Donut box open, gotten up to answer the phone with a chisel on our knee only to have it drop onto the floor and ruin the edge. (and then to make it worse, it was only a telemarketer!) Things like these happen to all of us and then we wonder why our tools keep getting dull. If we can learn to prevent these things from happening the life span of our tools will increase dramatically.
Things that can damage your edges
Sandpaper. Sandpaper is probably the worst on any edge. It contains the same Aluminum Oxide or Silicon carbide particles that help create the edge of your knife in the first place. When you carve a piece that will eventually need to be sanded, carve it as close to finished as you can without using sand paper. After you start sanding your carving, you really cannot go back to carving again. When you sand, you are leaving these sandpaper abrasive particles in and on your carving which, when you use your knife to touch up an area that has been sanded will abrade against the edge, thus dulling it.
Other tools. These tools most often have gone through an extensive Heat treating process to get them hard. When they bang against each other they will get dull.
Misuse of your tools. I've done this myself. I've gotten to the point where I can start sanding my carving and used my carving knife to... yes, slice up the sandpaper into smaller pieces. Don't do it. Have a junk knife to do this.
The table or bench. Tools roll off or get pushed off the table and onto the floor. (that darn cat!)
Put your knives on a tray with rubber drawer liner glued to the bottom to keep your tray from sliding. I purchased my lining at Home Depot for $2.50 a 6 ft. roll.
Store your knives and chisels together in the same compartment. You should have a compartment for each individual tool. When you store these tools in the same compartment the hard steel of these tools bang together as you are walking to the car after the carving club meeting and get dull.
Store sandpaper with your knives, put your sandpaper in a separate container. Those particles fall out into your bag or box and abrade your tools.
Have a junk knife in your bag. Use this knife to slice up your sandpaper, cut open the super glue or scrape the paint from your fingernails.
Put your tools back on or in places that prevent them from rolling off the table or into each other.
Keep a sheath on your tools. If you do this, you can store your tools together.
Sheaths- I've seen a lot of solutions.
You can use wine corks for your chisels and knives.
Woodcarving Illustrated has had projects to carve your own sheaths in the shape of thumbs, ducks etc.
Styrofoam- Just cut a block longer than your blade and stick it in.
FoamCore- Go to your local picture framer and ask for some foamcore cut offs. It is a styrene sheet with paper on both sides. It even comes in colors. You then can cut it to fit your tools.
Leather - glue up a piece of leather to wrap around your blade.
Phone books - I saw a lady at a show that rolled up a phonebook and taped it together to stick her knife blades into the end between the pages.