You already have a copyright on your designs. All you need to do is assert it. The way you assert it is to take all of your drawings, descriptions, etc., and write "Copyright (c) April 8th, 2000 by Edrozen" on every sheet and then sign your name below that. Of course, use the actual date on which you sign them, and use your legal name.
It wouldn't be a bad idea to get a friend who is somewhat knowledgable about knives (he doesn't have to be an expert, just knowledgeable enough to understand and appreciate what he's looking at) to review the designs and add the notation "Read and understood, April 8th, by Friend" on every sheet and then sign his name below. Again, use the actual date on which he signs and his legal name.
Next, the law will tend to treat your intellectual property in the same way you treat it. If you treat it as worthless doodles, then so will the courts. If you treat it as valuable designs, then so will the courts. So, treat your designs as valuable intellectual property. This means don't show them around to every Tom, Dick, and Harry. Show them only to people who have a reason to see them and then only after those people agree to keep what you show them confidential. Keep a record of who you show them to, what pages you showed that person, the date of the disclosure, why you disclosed to that person on that date, etc. Destroy any documents you're discarding. Keep any you're not in a safe container.
The real legal step is to patent your designs. Even if you don't think that there's a patentable innovation in your designs, you can still get a design patent on the design itself. Talk to a reputable patent attorney. If you already have a patent attorney, then you're all set. If the lawyer you mentioned is a business attorney, probate attorney, divorce attorney, your CDA, whatever, but not a specialist in patents and intellectual property law, then ask your attorney to recommend a good patent attorney in your area for you to handle this aspect of your legal needs.
Good Luck. I hope that at least one or two of your designs involve two handles that counter-rotate around the tang.
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Chuck
Balisongs -- because it don't mean a thing if it ain't got that swing!
http://www.balisongcollector.com