To flip the local orientation of surfaces
To flip the local surface orientation of surfaces, use the following procedure.
The default orientation of a surface local coordinate system is determined by the order of the nodes that form the surface vertices and the plane of the surface. The edge formed by the first two nodes selected (i.e., N1 and N2) define the direction of the local x axis. This procedure reverses the nodal order of the surface incidences, thus redefining the local x axis and reversing the direction of the local z axis.