Prevent laptop sliding around non-permanently, inexpensively

I don't know what you call it but when working on wood working projects there is a mat you can put the wood on and it will "not" slide anywhere. I have used it for other things as well. Low tech and inexpensive.

It is gray in color and feels like soft rubber. You can find it at Lowe's or most any hardware store just ask someone in the tool section.