Racking on a truss is an extra compartment on the roof used for storage. Racking can be constructed using wood or steel.
Racking carries the sole purpose of providing storage to items. Businesses that utilize steel racking store heavy items such as machines, homeowners use the extra space for keepsakes that cannot be left in the house.
The racking size on a structure depends on the shape of the truss. Racking on a wide arch-type truss is larger than racking on a narrow triangular-shaped truss.