Before random orbit sanders – and sanding discs – became all the rage, sandpaper was usually sold in rectangular sheets and 9”x11” was considered the standard size.

So, why 9”x11”? You guessed it; the size was driven by the needs of the electric sanders of the day.

When electric sanders first hit the market, they were produced to use one of two sizes of sandpaper: half-sheet or quarter-sheet. To make it simple for the end-user, they standardized the sheet size so that it was easy to cut and fit sandpaper to the sanders.

For example, the big silver Porter-Cable 505 is a half-sheet sander.

The Porter-Cable 330 was a quarter-sheet sander.

Because you knew whether your pad was a half- or quarter-sheet, you could easily determine your yield (either two or four usable pieces from each full sheet purchased).

Today, pad sanders still hold a place in many professional shops. Rectangular bases are still found on professional level air sanders and electric sanders. When used properly, they excel at sanding door panels and their 90-degree ends can get much further into the corners than any random orbit sander can, making them true work horses in a professional shop.