Screw the chain onto the end of the rod 'train'. Now, place the rod and chain assembly into the void you wish to route through. Take the magnet and screw it onto another rod. Using your final access point (plug socket, floor board etc), fish inside the void until the magnet connects with the chain. Once the connection is made, you can draw the chain and rod end out of the void, replace the chain with a cable handling attachment and draw the cable into place. Simple!
