Editing Rail transport modelling (section)

== Couplers and connectors ==
{{Main|Railway coupling#Model railway couplers}}
In addition to different scales, there are also different types of couplers for connecting cars, which are not compatible with each other.

In HO, the Americans standardized on horn-hook, or X2F couplers. Horn hook couplers have largely given way to a design known as a working knuckle coupler which was popularized by the Kadee Quality Products Co., and which has subsequently been emulated by a number of other manufactures in recent years. Working knuckle couplers are a closer approximation to the "automatic" couplers used on the prototype there and elsewhere. Also in HO, the European manufacturers have standardized, but on a coupler mount, not a coupler: many varieties of coupler can be plugged in (and out) of the NEM coupler box. None of the popular couplers has any resemblance to the prototype three-link chains generally used on the continent.

For British modellers, whose most popular scale is OO, the normal coupler is a tension-lock coupler, which, again has no pretence of replicating the usual prototype three-link chain couplers. Bachmann and more recently Hornby have begun to offer models fitted with NEM coupler pockets. This theoretically enables modellers of British railways to substitute any other NEM362 coupler, though many Bachmann models place the coupler pocket at the wrong height. A fairly common alternative is to use representations of chain couplings as found on the prototype, though these require large radius curves to be used to avoid derailments.

Other scales have similar ranges of non-compatible couplers available. In all scales couplers can be exchanged, with varying degrees of difficulty.