This sketchup vray video tutorial from MasterTuts, will show you how to apply the refraction layer perfectly in V Ray for SketchUp.
Refraction signifies the modification of direction of a ray of light that is transmitted at an angle from one medium to another. The refraction layer in vray is utilized to produce glass or translucent materials.
Go through the following article, to learn how to add and edit Refraction Layer. www.vray.com