Saw nibs have been present for hundreds of years. What is their purpose?
well, there may be more to it that you'd think. And definitely an interesting piece of trivia.
There are 2 types of nibs, either as something sticking out like on the picture in the question, or as a little notch.
There are multiple answers, ranging from:
- nothing, that's just for decoration
- this can be used to attach a blade guard (so you tie the strings around it and it won't slip)
- you can use it as a pivot point against a nail to draw a circle (you lock your pencil in between 2 teeth).
The explanation I'd always seen was that this "single tooth" could be used to create an initial nick in the wood to start the cut at a fairly precise place. Without that nick, the first cut has a tendency to slip sideways a bit, losing accuracy.
You could create the guide nick in other ways -- with a chisel, for example -- perhaps more accurately. But building it into the saw guarantees you'll have it when you need it.
I can't prove that was the original intent. But I can say that it seems to work when used that way. It's more a carpentry solution than a cabinetry solution, though, since it risks a bit more tear-out.
He seems to research historical things very well and he responded that neither he nor anyone else knows for sure. He said he had asked Roy Underhill (host of PBS's Woodwright's Shop) and a few others.
So, nobody knows for sure.
I always liked this answer
Some have said early handsaws had an auxiliary handle near the toe to guide the flexible saws and prevent them from bending. The nib is said by them to be a vestigial handle which had become ornamental.