Space bar

[2] Originally, (on early writers dating back to the late 19th century) the "bar" was literally a metal bar running across the full width of the keyboard (or even wider, and even surrounding it) that triggered the carriage advance without also firing any of the typebars towards the platen.

Later examples gradually shrank and developed into their current more ergonomic form as a wide, centrally located but otherwise apparently normal "key", as typewriter (and computer) keyboards began to incorporate additional function keys and were more deliberately "styled".

In some keyboards, both physical and specially virtual ones, the U+2423 ␣ OPEN BOX symbol is used to label the space bar.

Some early typewriter and particularly computer keyboards used a different method of inserting spaces, typically a smaller, less distinct "space" key which was also often set in a less central position, e.g. the Hansen Writing Ball, Hammond typewriters or the ZX Spectrum and Jupiter Ace ranges.

However these methods were also usually just one part of similarly idiosyncratic full keyboard layouts, designed more to cope with particular technical requirements or limitations than with any sense of user friendliness and as such met with limited success, sometimes being dropped even on later models in the same line (e.g. Sinclair Spectrum 128k and "Plus" lines, which adopted more "normally styled" keyboards with plastic keytops and a wide, central space bar in place of the earlier rubber "chiclet" keys and small, offset space key).