O14 is a standard for accurate modelling of prototype 2ft narrow gauge railways in 7mm:ft scale (1:43.5) using 14mm gauge model track. As such O14 should be regarded as the 2ft narrow gauge equivalent of Scale 7 for 7mm Standard Gauge.
Note O14 is the official term that should be used, not O-14 and definitely not On14. It is not to be confused with On2 which is a US based standard in ¼”:ft scale (1:48) on ½” gauge model track – the same finescale objective but on a different scale.
In practice the actual gauge of nominal 2ft gauge railways varied considerably. 2ft (610mm) was usually the norm for industrial systems with the larger mainline style railways typically being of 1′ 11 ½” (600mm) gauge. This latter gauge was used by both sides for the extensive military railways in WWI and much of this equipment found further use elsewhere after the war. Even those of the same exact gauge often had sometimes incompatible variations in back to back and flange way dimensions. Therefore for modelling it is recommended to use the same O14 standards for all such variations as this will give you correct looking track which will be almost exactly to scale especially with regards to flangeways etc.
Trade support originated with Roy Link who also defined the O14 standards. Roy Link has also provided support to O14 for many years through the excellent magazine Narrow Gauge and Industrial Railway Modelling Review.
Other 7mm manufacturers are increasingly providing O14 options as noted here: O14 Manufacturers and Suppliers. We would like to encourage traders to post details on this site about any products of interest to O14 modellers.