I have decided on the desirability of carrying a fixed blade knife mainly for those rare occasions when it is necessary to split branches to produce dry kindling and shave them to produce ‘excelsior’ (wood shavings) which are the best fire starter. Lighting a fire when it is very wet and cold is the most important time – and can save your life. You can’t really do this with a folder or any other of the ultra-light hiking options (eg Micro Leatherman – 50 grams, or Swiss card – 25 grams (though both are excellent multi tools for a variety of purposes; the Leatherman has the best toe-nail cutting scissors in the world!)
You have to be able to split dry branches you can break into @ six inch pieces over your knee. (The lightest hatchet/machete is too heavy for emergency-only carrying at 4-500 grams – though this is the best one: http://www.theultralighthiker.com/the-worlds-greatest-machete/ as it will cut blackberries EASILY). You have to be able to hold the handle and tap on the end of the blade with another piece of wood, so the blade needs to be at least 3” long, and clearly this procedure would put a lot of stress on a folder.
These two sites have some very light fixed blade knives (http://www.gofastandlight.com/Knives-Saws/products/20/ & http://kestrelknives.com/products/) Kestrel’s ‘Ultralighter’ would be hard to beat @ 11.6 grams though a 2 ¼” blade is quite minimalist, but should do the job in an emergency and would still butcher game or fillet a fish quite satisfactorily. It is a bit pricey at $100 though, so I might opt to carry a little more weight and try out eg the Ka-Bar Adventure Piggyback Knife just over an ounce & $8.88 or the Ka-Bar ZK Acheron Skeleton Knife (with a 3 ½” blade also @30 grams) & $9.39 or the Mora Scout @ 85 grams including sheath – which is a bit heavy -$16.89. (Update: I bought both these Ka-Bar knives and they are excellent! Della is carrying one, and I, the other)
Pictured: My personal favourite: Ka-Bar’s Johnson Adventure Piggyback Knife at US$11.59 and 23 grams.