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The Jig

Created Dec 22, 2024 crafttools

A jig is a fixture that holds work and guides tools. In woodworking: a crosscut sled that clamps to the table saw and guides every 90-degree cut. In manufacturing: the steel form that positions car doors for welding. The jig takes the skill out of the individual operation and embeds it in the system.

This is the workmanship of certainty made physical — David Pye‘s name for work whose outcome is fixed in advance by the tool or template, no longer staked on the maker’s care in the moment. The jig converts a risky operation into a reliable one, and the tolerance it holds is the tolerance every future part inherits.


Building a crosscut sled takes four hours. The sled itself is plywood and runners. But once built, every subsequent cut takes eight seconds and comes out true to 0.002 inches. The four hours amortize across hundreds of future cuts.

This is the logic of fixtures: spend time once to save time forever. The investment compounds because the jig outlasts any single project.


Software has the same pattern. The deploy pipeline takes a Saturday to configure. After that, shipping takes one command and 90 seconds. The test harness takes an afternoon; every subsequent test runs on save. The script that generates boilerplate takes 20 minutes; the next month of features flows through it.

The friction of manual process disappears into automation. The precision of expert judgment disappears into tooling — the maker’s tacit skill externalized into a thing that holds the standard whether or not anyone remembers why.


The thing that makes the thing matters more than the thing itself. A sled outlasts a hundred projects. A pipeline ships a thousand features.

Build the jig first.