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).