Timber used for dunnage must be all of the following EXCEPT:

Timber used between tiedowns and cargo must be strong enough not to split or be crushed.
Any timber used should be properly seasoned, and free of rot or decay.
The grain should run lengthwise along the timber when it is used for structural purposes like blocking and bracing.
Timber should be free of knots, knotholes and splits that may affect its strength or interfere with nailing.