It is not absolutely necessary, but it is recommended. It protects the edges of your floor covering and it rounds off the overall appearanc We have two 2 types of frame: STAINLESS STEEL, 15 X 20 X 3 MM, WITH ROUNDED EDGES SPEZIAL ANGLE FRAME 15 ALUMINIUM, 15 X 20 X 3 MM We recommend using any of these 2 SPEZIAL angle frames for the installation of all Top Clean matting systems to ensure optimum fixation and easy release for cleaning purposes. Frame, corner connections and screws are made of one material, stainless steel or aluminium, to prevent corrosion. Frames are mitre-cut and ready for screw connection.