First turn off the central heating system and drain a radiator before moving it to gain access to the wall behind. Place rags under the retaining nuts on each side of the radiator as a safeguard against possible leakage, and loosen the nuts. Remove the radiator from the wall brackets and swing it down on to a wooden block. Tighten the retaining nuts.
When the decorating has been completed, fix the radiator back in position. Take care, however, not to tighten the nuts too much: otherwise the packing in the joints will be damaged and the radiator may start to leak.