The rails are joined by fish plates at the rail ends or at a later state by welds. They are intended to carry over the forces on the rails from one end of the rail to the next one. The fish plates must connect the rails so that the rail running edge and rail running surface exactly match in height and direction and cannot be tilted.
A rail joint which is located directly on top of a sleeper is called a fixed joint. However, should the joint lie between two sleepers this is called a floating joint. If two adjacent sleepers are connected at the rail joint (so-called joint sleeper or double sleeper), it is a broad sleeper joint (which is no longer installed today).
Depending on the cross-section of the individual fish plates, a distinction is made between flat, angle and double angled fish plates. In general, all fish plates have four holes for the securing of bolts in the threaded connection. But there are also so-called long fish plates (length 900 mm) they have 6 holes for the bolts.
Compromise fish plates:
Used with different rail heights or when there is wear on the rail head.
Standard fish plates:
Use with same rail height (e.g. new rails).
Belly fish plates
Used for broken rails and on welds.
Emergency fish plating
If rails are to be connected to each other, a solid and secure end of these rail joints is required. With two flat fish plates, the rails are joined in the correct position. These flat fish plates are in turn held by so-called emergency fish plates.
You can find suitable specialist literature to the topic here:
The Basic Principles of Mechanised Track Maintenance
This book is dedicated to the many people involved in the day to day planning and performance of track maintenance activities. Providing a practical approach to everyday challenges in mechanised track maintenance, it is not just intended as a theoretical approach to the track system.
Railways aim at transporting people and freight safely, rapidly, regularly, comfortably and on time from one place to another. This book is directed to track infrastructure departments contributing to the above objective by ensuring the track infrastructure’s reliability, availability, maintainability and safety – denoted by the acronym RAMS. Regular, effective and affordable track maintenance enable RAMS to be achieved.