Microtubule inner protein involved in the attachment of outer dynein arms (ODAs) to dynein-decorated doublet microtubules (DMTs) in cilia axoneme, which is required for motile cilia beating (PubMed:36191189). Functions at the initial step of left-right asymmetry specification of the visceral organs. . This is the function of PIERCE1 (piercer of microtubule wall 1, ENSG00000160345).