Editing HO scale (section)

===Couplers===
A hook-and-loop coupler originally developed by Märklin became an [[Normen Europäischer Modellbahnen|NEM]] standard and is still widely used. More recently,{{When|date=October 2022}} manufacturers, including Fleischmann and Märklin, developed close couplers that on straight track have the buffers almost touching, more like the prototype. On curves a sliding mechanism allows the couplers to move away from the buffer frame providing the additional clearance necessary.

Most couplers provide pre-uncoupling, whereby a train may reverse over a raised uncoupler and some time later change direction leaving the train (or selected cars) behind.

Another NEM standard is the coupler pocket, which the individual coupler slots into. The majority of models provide this pocket, meaning that it is very simple to exchange one coupler type for another, or to replace damaged couplers.

In North America, all train sets/kits used to come with the "X2F" or "Horn Hook" coupler until [[Kadee]] came out with the No.&nbsp;5 coupler.  After Kadee's patent ran out, other manufacturers made duplicates of the KD No.&nbsp;5 until KD brought out the scale-accurate No.&nbsp;58 coupler, and everyone else followed suit.

In Australia, older models produced by Lima and Powerline traditionally used NEM hook-and-loop couplers, however almost all models since the mid-1990s use Kadee or compatible couplers such as Bachmann E-Z Mate. Older Australian-market train sets manufactured by Tyco, Life-Like and Bachmann used the same horn hook couplers as their American counterparts.