Not really a tool but certainly a device that few woodworkers should leave out of their tool box.
Prior to the mid 1800s nails were forged or cut. These nails began to fall out of vogue during the19th century as cheaper steel or wire nails took over.
However, cut nails grip better than wire nails.
When a nail is hammered home the fibres of wood are forced downwards. To remove a nail the force has to be greated that the hold of the wood fibres acting like barbs/shark teeth on the surface.
Modern nails are round or oval and tapered only at the end, therefore wood fibres in contact with the nail bend downwards. Cut nails on the other hand taper from thick at the head to thin at the tip. The deeper the nail is driven into the wood the greater the wood fibres are bent thus increasing the force needed to remove the nail.
The other advantage is that with their squared off ends there is less likelihood of the wood splitting as the nail is driven in. Wire nails need their points dulled to achieve the same effect.
So. I was quite excited when I found these 9 assorted boxes (4Kg) of cut nails for $8.00. How could anyone resist!?