Slides edges along the surface.
The same operation can easily be implemented in VEX using half edges. This was implemented before VEX had half edges.
Edges in Houdini are very expensive computationally, but half edges provide a reasonable alternative for these kinds of operations.
https://www.dropbox.com/s/b71smfvc4wzhaa0/SlideEdges_SOP_Animatrix.otl?dl=1