[zhōng liú dǐ zhù]
mainstay; a pillar [a firm] rock in midstream; a tower of strength; stand firm as a rock in mid-stream; the chief cornerstone; the solitary rock in a turbulent stream
The five engineers of real learning are the mainstays of the small factory.
那五位具有真才实学的工程师是这个小厂的中流砥柱。