The top and bottom rails of a trussed beam are joined by what?

The top and bottom rails of a trussed beam are joined by truss blocks. Truss blocks serve as the crucial structural components that connect the top and bottom chords of a truss system, allowing for effective load distribution and stability. These blocks are designed to withstand various forces and help maintain the integrity of the truss by ensuring that the top and bottom members remain in the correct alignment and position under load. This design is essential in creating a strong and reliable truss structure, which is widely used in various types of construction, particularly within roof and floor systems in buildings.

In this context, considering the other options: tie rods are typically used for tension support in structures, |-beams are not a recognized term within truss terminology, and A.-plates refer to connecting plates that may serve different functions but are not specific to the joining of top and bottom rails. Thus, truss blocks are the appropriate components for this particular structural connection.