Its a piece of cloth impregnated with some sticky substance. Dust sticks to it when you wipe it over a surface. It won't get dust out of crevices though so it's best to vacuum first then use a tack rag.
Originally Posted by pcatterall
You can buy tack rags at any decent decorators' supplies shop or on-line. I use Liberon but there are others.
They can last a long time and it's best to keep them in an airtight container between uses to stop them drying out.
You can also make your own http://www.thesuperhandyman.com/?page_id=116
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