Cabling and wiring often form the coupling path between the source of electromagnetic interference and the victim who is susceptible against this interference. To reduce the coupling of and between cabling for internal and external fields the use of parallel earthing conductors (PECs) is recommended. This chapter discusses tubular structures and nonmagnetic cable trays. Normally, cabling has to span stretches which are longer than a single length of a cable tray. Compared to cable shields, however, shallow cable trays still provide very good protection. The transfer impedance concept can be extended to characterize the Electromagnetic Compatibility (EMC) performance of PECs. The transfer impedance of the copper tube is at low frequencies nearly identical to the closed tube. The amount of coupling with the magnetic field depends on the position of the inner conductor. The chapter concludes that an additional structure only provides additional protection if it has lower or similar transfer impedance as the cable it has to protect.