In Hotels, the room service go to great lengths to fold the towels in a manner that all the edges are even and tidy. It’s the edges that can ruin the best laid plans.
Towelbox isn’t about the radiator, its about the towel, the contents, the thing the radiator is there for.
It is a radiator the same size as the towel it holds. It essentially creates a frame around the towel to make the most elegant composition.