Tools required :- Sharp knife or scissors and a tape measure.
Heat from radiators can be partially absorbed by the wall behind them, more so if the radiator is on an outside wall.
Radiator foil is simply foil attached to a thin layer of polystyrene. It comes in two forms, the first is on a roll, the second is in the form of tiles, both are around 500mm in width and usually come with sticky pads to attach the foil to the wall behind the radiator.
It works by reflecting the heat from the back of the radiator away from the wall thus making the radiator more efficient and therefore heating costs should be reduced.
The foil roll and foil tiles are available at good DIY stores and would cost approximately £10 per average size radiator.