I think the rocker panels are held on by plastic pop rivit type fastners underneath the car that break easily when you take them off. Plus underneath the black plastic cover on the top of the rocker panel, there may be some more fastners. Mine have been off at least three times, cause they get scuffed up easily. But I just sent the car to the paint guy in the body shop and the came back painted. Not too very expensive.
I think a "special tool" is needed to pop the "special fasteners" to reattach the rocker panels.