A side rail assembly useful for securing a deck of a scaffold comprises a side rail configured to be supported between two ladder frames in first and second orientations. The side rail includes first and second support surfaces for supporting the deck in the first and second orientations, respectively. First and second vertically aligned slots are formed in respective opposing surfaces of the side rail. The side rail assembly further comprises a locking pin assembly comprising a shaft, a locking tab, and a biasing member to bias the locking tab into engagement with the deck and secure the deck against one of the support surfaces of the side rail depending on the orientation. The locking pin assembly is configured to be removably engaged with the first and second slots of the side rail in both the first and second orientations.