"Ganging" refers to the act of putting multiple images, either the same image or different images, onto one transfer paper. For instance, if you need to print 1,000 of the same 4 X 4 left-chest image, you could theoretically fit two side by side on a 9" X 12.75" sheet. Then you only need to print, or order, 500 sheets rather than 1,000 individual transfers. Ganging can be more cost-effective depending on the size of the image, the number of colors being printed, or the quantity of that specific order.
Source: Julie Hawthorne