Printing Double-sided Patterns

Some patterns require you to make double-sided prints. Since most of us don't have printers that can handle "full duplex" printing, we have to print the first side of the pattern, stick the paper back into the printer upside down and print the second side.
Sounds simple? Believe it or not, I still make plenty of mistakes putting the paper back into the printer in the correct orientation. Here is the easiest way I have found to make a fool-proof double-sided print.

Steps

1. Make a light pencil mark on the left hand corner of the paper in the paper tray of your printer before you print the first side of the pattern. (Leave the paper in the tray when you do it.)
   
2. Print the first side.
   
3. Place the paper back into the same paper tray with the pencil mark on the right-hand corner facing down.
   
4. Print the second side.