A 1/2 sheet sander is so called because its sanding plate is the same size as half of a standard sheet of sandpaper. Standard sanding sheets can be cut up and fixed to the sanding plate or alternatively purpose built sanding sheets are available which come cut to the correct size and pre-punched with dust extraction holes (most 1/2 sheet sanders are also supplied with tools that enable you to do this yourself). The 1/2 sheet sander is a type of Orbital Sander, also known as a Finishing Sander. It has a much less agressive action than belt sanders or random orbit sanders, so is not recommended for heavy stock removal and is instead most commonly used for finishing applications like fine sanding, chamfering edges and sanding in between coats of varnish. It is also commonly used in situations where a sanding disc would be innefective, for example sanding up against straight borders. The basic orbital action of a 1/2 sheet sander means it typically produces a slightly inferior finish to that of random orbital machines.
1/2 Sheet Sander Safety:
Some materials can produce hazardous or irritating dusts when sanded, so make sure to wear suitable clothing and respiratory protection.