Ship building.

[xoxoxoBruce]

The wiki article on building the WW II Liberty ships describes how the US redesigned the UK model, changing construction from riveted to welded plates and a different propulsion system eliminating the need for difficult to build reduction gears.
The welded plates became problematic, but was ironed out in later construction techniques post Liberty program.

The first ships required about 230 days to build (Patrick Henry took 244 days), but the average eventually dropped to 42 days. The record was set by SS Robert E. Peary, which was launched 4 days and 15½ hours after the keel was laid, although this publicity stunt was not repeated: in fact much fitting-out and other work remained to be done after the Peary was launched. The ships were made assembly-line style, from prefabricated sections. In 1943, three Liberty ships were completed daily.