Indicates the difference with a "sheet" and a "pane"
see the double selvedge on
right hand side of this pane.https://www.linns.com/news/postal-u...iature-.html
One of the most misunderstood and misused terms in stamp collecting is "sheet of stamps."
In common parlance, what collectors and noncollectors alike often refer to as a sheet of stamps is in fact a pane of stamps.
The sheet is the complete printing unit of stamps as it comes off the press, either as a sheet or part of a long roll called a web.
Sheets usually comprise two to 12 (or more) panes. Panes are the units into which sheets are divided before delivery to the post office for sale. Many recent United States commemorative stamps, for example, have been produced in 240 stamp sheets that were divided into 12 panes of 20 stamps each.
The U.S. Postal Service (and its predecessor the U.S. Post Office Department) have occasionally sold full uncut sheets of stamps to the public. A sheet of 180 1997 U.S. 32¢ Classic Movie Monsters stamps (Scott 3168-72) is shown in Figure 1. Notice that there are nine panes of 20 stamps each in the sheet.