Check Wood Irregularity : A separation of the wood along the fiber direction that usually extends across the rings of annual growth and commonly results from stresses set up in the wood during seasoning
NFPA 1931 Standard for Manufacturer's Design of Fire Department Ground Ladders, 2004 ed. https://www.nfpa.org/assets/files/AboutTheCodes/19 32/1932-A2004-ROP.pdf, (Std: Mfg Design of Fr Dept Gr Ladr - Amer) {419 NFC}