In article ,
says...
Just decorating our house, and the radiators previously had wooden shelves
bonded to the top of them with some kind of sealant. Is this method ok to
use, or can it cause problems with hot airflow etc.? Or should I use
brackets to hook the shelves over like the ones you can purchase? If I
should go for the brackets, is there anywhere that sells them on their own?
I'd prefer to reuse the shelves we have, rather than buy new ones esp as one
is 2metres!

Why not just use shelf brackets fixed to the wall?