When considering a pocket knife to carry several things are important to me. Perhaps size and weight are the most significant. If the knife is too large or heavy you will end up leaving it home on your dresser rather than tossing it into your pocket or purse.

Many pocket knives have more than one blade. This could be handy I guess if the second blade is a different shape or design than the first. For example, if the second blade is considerably more pointed than the first and could be used for different tasks. In general though, I don’t find second blades terribly useful.

Locking blades are a different story. Many modern knives have some sort of locking mechanism that snaps into place and keeps the blade from folding back into the handle while in use. This can be an important feature as you might be surprised how many times you are working with the knife, and all of the sudden feel it give way, with the blade coming dangerously close to your fingers as it closes. For really casual use this might not be a necessary feature. In another post, (pocket knife introduction) I mentioned the knife I carry much of the time, and it does not lock. But if you are likely to use the knife much at all, getting a blade that locks is incredibly handy, and can be much safer.

Blade length is related to overall size and weight. For almost all everyday uses a blade of 2 inches is perfectly fine. I would not recommend carrying a blade of more than 4 inches as the knife starts getting big and heavy, and the extra length is really not needed in most everyday uses.

If you really expect to use the knife for more moderate- or heavy-duty uses, a heavier knife is warranted. Get the right tool for the job. Outdoors adventurers, hunters, fishers, campers and the like will likely use the knife for everything like cutting rope, digging into rocks (yes, I have), prying open cans, whittling marshmallow sticks, slicing cheese and lunch meat, and a host of other activities. For these sorts of uses a larger, stouter blade is needed. If you intend to carry it in your pocket, I still would not recommend a blade longer than about 4 inches. Much longer and the knife is just too uncomfortable to carry.

If you are expecting much more heavy use you might want to consider a fixed blade hunting knife, the kind with a sheath that does not fold at all. The fixed blade is a single piece of steel with the handle, making it much stronger overall. Pocket knives are great to have handy, but there are limitations to what you should expect them to do.