We've said over and over that a good fixed-blade knife is central to any survival kit. Also, the key to any knife is that it must be sharp enough to cut through whatever material you're working on. In short-term survival situations, this is easy enough, since you can simply sharpen your blade at home and have it ready to use. In longer-term survival situations, however, even the sharpest and most durable blades will eventually dull and chip.
To keep your knife performing as it should, you may need to improvise and sharpen it in the field.
The Sierra Trading Post YouTube channel created the video below to demonstrate 5 ways to sharpen a blade without the aid of a sharpener. Check it out, and see if you've considered any of these methods before.
For those who can't watch the video, here's a list of the techniques used: