A planar carrier for mounting on a rim of a steering wheel without wrinkles, the planar carrier including a portion of planar flexible foil of roughly rectangular shape having two longitudinal sides and two lateral sides, wherein the length B of the lateral sides is 0.96 to 1.00 times the perimeter of the rim, and wherein N cut-outs per unit length are provided on each of the longitudinal sides. The cut-outs of one side are located in a staggered fashion relative to opposing cut-out portions on the opposite side. The optimum shape and size of the cut-outs may be determined as described. The planar carrier may be implemented as a heat carrier, a heating device and/or a sensing device.