I use a "chain saw" tool quite a bit. I don't remember the brand and the container is long gone. However there is quite a bit of variation between the brands. Look at several and choose carefully. I would have to look at them together to see the differences (can't remember) but there are obvious differences.

Most of the old time woods guys I know carry a couple or three standard bow saw blades fastened to their pack. They make what they call a "H" frame when needed. That is the type of frame with two vertical bars and a center horizontal bar like a capital H. The blade fastens to the lower end of the vertical and a rope goes between the top ends of the vertical. The rope is a loop and a stick goes in the loop. Twisting it makes the rope shorter and puts tension on the blade. The stick is long enough so that it can be hooked against the center bar to keep it from unwinding.

I have seen a guy make one in about 5 minutes. When done he has a fully functional full size saw and can do some serious cutting. Well worth the 5 minutes to make.

Nomad