Files and hacksaws
Files and hacksaws were two tools that were around the house when I was a kid, and puzzled me quite a bit: I couldn’t figure out how anybody did much with them. Later I learned: the secret is in what was missing: the vise. The piece being filed or hacksawed should be clamped firmly in a heavy, solid vise which is bolted down tightly — or some other arrangement that is equally rigid. (If the workpiece is big and heavy enough, nothing is needed to hold it, but that’s uncommon.) Then you can apply the sort of force that is needed to remove metal fast, without the workpiece escaping or getting into a mutual dance of vibration with the cutting tool.
There are of course various fine points to using these tools, but the workholding arrangement is what makes the difference between usability and unusability. It is not out of place to have a vise that costs more than all one’s files and hacksaws put together and weighs ten times as much as them.
(This is one of those things that people with a mechanical background know so well that they couldn’t even imagine not knowing it; but that still leaves the other >95% of the population.)
Oh, and while vise manufacturers seem to love to make toothy vise jaws, for civilized work a flat-faced jaw is usually best; that way it’s holding the workpiece with clamping force, not by digging its teeth in and damaging the surface.