*"fixed"*.

# Choosing Reference Faces

Now lets apply some of the key concepts of earlier posts. In practical terms, if the imperfect timber we are using has two relatively square surfaces it is easier to imagine that the perfect timber inside begins on these two surfaces(these are the reference faces) and the remaining perfect faces lie within the remaining imperfect timber. If we align the reference faces of the timber with the reference planes of the building then the important dimensions and functions of the building/structure will be