3 for instance several heating element receiving cavities 3 may be configured to provide a frictional fit for holding a heating element 5 while other heating element receiving cavities 3 may be configured to merely contain a heating element 5 in any event the underlayment 1 can include one or more configurations of heating element receiving cavity 3 fig5 shows a plan view of routing hubs 2 of an underlayment 1 in accordance with a first embodiment of the present disclosure as described above the protrusions 2 a base material 6 and or other features of the underlayment 1 may include a number of cutouts 10 or holes in some embodiments the cutouts 10 can extend at least partially into the protrusion 2 a base material 6 and or the underlayment 1 in some embodiments the cutouts 10 are shown as extending at least partially into at least one side of at least one protrusion 2 a fig6 shows a plan view of routing hubs 2 of an underlayment 1 in accordance with a second embodiment of the present disclosure the underlayment 1 section includes a number of routing hubs 2 comprising four protrusions 2 a arranged in an equally spaced circular array about an array axis 2 b in a matrix configuration a sample routing 4 of the heating element 5 is shown in fig6 in particular the heating element section 5 shown runs along the y direction of the first column of routing hubs 2 proceeds around the routing hub 2 in the second row and first column 1 2 and along the negative y direction between the first and second columns and then proceeds diagonally through the heating element receiving cavity.