This post is my attempt to explain how they are different and to give a simple device that one might construct out of "found materials".
Native or local materials are the geological resources (soil, rock, water, wind) or biological resources (plants, mammals, fish, birds) that are available within, say, a half day's walking distance.
Found materials are materials that are not local or native but are ubiquitous and easily obtained.
Examples of found materials might be things like railroad spikes, screwdrivers, electrical wire, microwave transformers, batteries, metal grill work (like refrigerator shelving), baling twine and the like. I dare say that you could go into any house in America and find multiple examples of each item...or reasonably close substitutes.
So what might an enterprising person MacGyver together using found materials?
In dire circumstances normal "sporting" methods of take will not be efficient methods of collecting food. Fishing consumes much time for the food collected. During periods of social unrest the fisherman is exposed to risk. Exceptions might be trot lines, except in some states (Michigan is one of them) that outlaw unattended fish lines.
Chumming a shallow area with a gallon of soaked/sprouted/soured corn for a few nights in a row will cause many "rough" fish to concentrate in the area. One might be able to harvest hundreds of pounds of fish using this method.