With the exception of special unit width founts the brass width of linecaster matrices is measured in thousandths of an inch which is then converted into whatever unit of measurement is used by the perforator; this may be either 1/64th, 1/96th, 1/128th of a pica or 18, 32, or 64 units of set.
Source: wiktionary
The following are standard linecaster operating units either fitted to the linecaster keyboard or free-standing.
Source: wiktionary
This length of perforated paper tape was then fed, by another operator, into a linecaster machine which automatically read the perforation codes on the paper tape and made the metal casts accordingly.
Source: wiktionary