Final answer:
A cord in a roof truss refers to the horizontal members that provide support and stability. The upper cord is the top horizontal member, and the lower cord is the bottom horizontal member. They are connected to the vertical and diagonal members to form a rigid structure.
Step-by-step explanation:
In roof trusses, a cord refers to the horizontal members of the truss that span from one end to the other. They are usually located on the top and bottom of the truss and provide support and stability.
The upper cord is the top horizontal member of the truss, while the lower cord is the bottom horizontal member. These cords are connected to the vertical and diagonal members of the truss to form a strong and rigid structure.
For example, in a typical triangular roof truss, the cords represent the top and bottom edges of the triangle, while the vertical and diagonal members form the interior angles.