Hatrack (French: Porte‑chapeaux) is a readymade conceived by Marcel Duchamp in New York around 1916–1917. The original object is lost. The work is known through a small number of representations—two shadows (1918), a studio photograph (1916–17, published later) and a derived print (1941), plus a 1964 blueprint and a 1964 wood edition produced under the direction of Duchamp by Arturo Schwarz.[1] Taken together, these “snapshots” do not agree in hook‑count, curvature, or overall geometry. As a result, descriptions in institutional cataloguing, auction metadata, and secondary literature diverge.
A systematized audit was undertaken by the Art Science Research Laboratory in 1997 using digital/physical models and forensic photographs to catalogue the inconsistencies within Duchamp’s own emphasis on seriality and a non‐retinal, “scientific” perspective.
Meta-Wiki
Readymades of Marcel Duchamp (wikipedia)
Diffs of Marcel Duchamp (reverted on Wikipedia)
Tout-fait (as referenced on wikipedia)
Grokipedia
Readymades on Grokipedia ("adapted" from Wikipedia)
Groks of Marcel Duchamp (AI edits)
Duchamp Research Portal
Illustrations
1; 2A–F; 3A–B; 4A–C; 5–6; 7A–D; 8A; 9; 10–11; 12A–D; 13A–C; 14A–E; 15A–B; 16A–B; 17–18; 19A–B; 20A–C; 21A–B; 22A–C; 23A–E; 23F–I; 24A–C; 25A–B; 26A–B; 27–32; 33A–B; 34A–H; 35A–E; 36A–E; 37A–D; 38A–B; 39A; 40A–F; 41A–D; 42A–D; 43A–C; 44A–B; 45A–C; 46A–C; 47A–B; 48; 49A–D; 50A–B; 51A–G; 52A–F; 53–54A–C; 54D; 55; 56A–B; 57A–C; 59–60; 61–62.
toutfait.com
References
Rhonda Roland Shearer, Stephen Jay Gould et. al., “Why the Hatrack is and/or is not Readymade,” 
Tout‑Fait. (2000; updated 2019).