A "house rule" when you are playing Risk and run out of Infantry, (worth 1), but have calvary (worth 5) and artillery (worth 10). Therefore, you have to manipulate "Manchange" with your adversary. When desperate not to "over
bet" on a territory you
may loose, you can negotiate trades, even (1 for 1) or "rough trade" (3 for 5) or (7 for 10).