Design website Core77 has an article about different ways to use a wooden pencil to the very end. First, though, take a look at this parsimonious person's pencil, which represents the cheapest and arguably easiest way to extend the life of a pencil:
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If you can't deal with a pencil this small, the article has other suggestions: pencil extenders (I can vouch for them), gluing a sub onto a new pencil, and using a remarkable Japanese pencil-joining tool call the Tsunago:
