The general opinion that I've found is that rebar is where recycled steel goes the 3rd or 4th time through the loop. Quality varies greatly, and some is barely acceptable as rebar, never mind anything else. More specifically, rebar doesn't have enough carbon in it to be hard enough for a knife blade. The CS torpedo is a medium carbon steel, but it still has more than rebar. Of course, knives were once made of copper, so you could grind a point on some rebar of appropriate length and have a poor mans torpedo. Just dont expect too much out of the point in terms of maintaining its shape.