This is a simple model inspired by the Secretlab Magnetic Cable Anchor that is used for the Secretlab Magnus desks to anchor cables to a metal surface, but this model has two tunnels for twice the cable anchoring as opposed to one. I never purchased any of the original anchors so I did my best guess at dimensions and made sure the inner tunnel was able to support various cable ends without them slipping through (Apple's Lightning cable being one of the skinnier cable ends). I attached three 20x5x2mm magnets (one for each leg) with glue after print completion.

I also created a single tunnel version here.