While simple, the strength and affordability of this design is unmatched. As its name implies, is the most truss most frequently used in timber framing today and in the past. You can tell it is a common truss by the lower tie beam joining with the two rafters forming the triangle.
The common truss is the most basic load-bearing truss and is useful in a wide variety of applications. It forms a simple triangle, and is often used as a secondary load-bearing component to some of the more aesthetically appealing truss designs.