Required for assembly of dynein regulatory complex (DRC) and inner dynein arm (IDA) complexes, which are responsible for ciliary beat regulation, thereby playing a central role in motility in cilia and flagella (PubMed:21131972). Probably acts together with CCDC40 to form a molecular ruler that determines the 96 nanometer (nm) repeat length and arrangements of components in cilia and flagella (By similarity). Not required for outer dynein arm complexes assembly (PubMed:21131972). {ECO:0000250|UniProtKB:A8IQT2, ECO:0000269|PubMed:21131972}. This is the function of CCDC39 (coiled-coil domain 39 molecular ruler complex subunit, Ensembl gene identifier ENSG00000284862).