Using barbless hooks when practicing catch and release has become increasingly popular, and in some states, required by law for some fisheries. Many fly anglers either use exclusively non-barbed hooks or carry small pliers or forceps to smash down the barb as needed while fishing. If you're part of the later group and would rather not carry surgical instruments or hand-tools, you can easily modify your fingernail clippers (the one's you use for trimming mono line) so they'll also work to de-barb hooks.

Use a thin file to dull one side of the clipper jaws.

Use a small, thin file (a fingernail file will work) to dull one side of the clipper jaws. A few passes with the file is all that is required to take the edge off. Leave the other side sharp for trimming leader and tippet material. A small dab of paint can be applied as desired to indicate which side is which.

Create a groove in the dull side by crimping the barb of a large, heavy-wire hook.

Choose a large, heavy weight hook and use the de-barb side of the clippers to clamp down on the hook's barb and smash it flat against the point. This not only de-barbs the hook but further dulls and creates grooves in the clipper's edge. Repeat the procedure a number of times. The edge must be dull to keep from cutting into the metal hook and the grooves will help hold smaller hooks in place during de-barbing.

The clippers can now cut monofilament and crimp the barb on any size hook.

The clippers are now a combo trimming and hook de-barbing tool that takes up very little space but is effective for smashing down the barbs on almost all sizes of angling hooks.