After K.A.C. Creswell, Early Muslim Architecture, vol. 2 (1940)

Enormous wooden beams throughout the mosque serve a variety of structural and aesthetic functions. The tie beams (red) on the nave ceiling that support the roof were covered with carved or painted panels and were adorned with elegantly carved cypress boards on their ends. Bond timbers (blue) were built into the arcade walls that separate the aisles and the nave. The timbers were placed in tiers parallel to the ground above the column capitals, under each row of upper windows, and beneath the ceiling tie beams. Additional smaller beams (not indicated here) removed from other sections of the mosque also predate the construction of Al-Aqsa and show signs of secondary and tertiary use.