The Rest Position SOP creates an attribute based on the surface normals that allows a shader to stick to a deforming surface.
All primitives support the rest attribute, but, in the case of quadric primitives (circle, tube, sphere and metaball primitives), the rest position is only translational. This means that rest normals will not work correctly for these primitive types either.
Use the Rest Position SOP only when you are deforming your geometry and you are assigning volumetric or solid materials/patterns in your shader.
Rest normals are required if feathering is used on polygons and meshes in Mantra. NURBs/Beziers will use the rest position to compute the correct resting normals.
It will be necessary to render the setup in order to see the effect.