run in

In letterpress and hot metal composition, run in means to push text or spacing material together to eliminate blank areas that would otherwise appear on the printed page. It is a corrective technique applied during makeup, the stage where composed type is arranged into pages and locked into the chase before printing.

The need to run in arises when a page layout leaves unwanted gaps, typically at the end of paragraphs, in narrow columns, or where word spacing has created irregular white areas. A compositor uses a furniture rule or bodkin to apply gentle pressure, compressing the spacing material (usually lead or copper strips between lines, or word spaces within lines) so that text shifts to fill the void. The aim is a visually even page without awkward rivers of white space.

When run in becomes necessary

Hot metal linotype and monotype composition can produce pages where the last line of a paragraph sits too high, leaving a deep blank at the bottom, or where justified text leaves visible holes. Running in is gentler than resetting the affected passage and faster than adjusting word spacing across multiple lines. However, excessive compression risks damaging type or creating illegible letter spacing, so restraint is essential.

The term reflects the direction of the correction: type and spacing are moved inward, closing gaps rather than expanding them. This differs from leading out, which adds space between lines. Both are operations performed cold, after metal has cooled and solidified, making them manual and labor-intensive. Modern offset printing eliminated the need for run in, since page makeup occurs digitally and spacing can be adjusted before film or plates are made.