(为获利而)脚踏两只船, 使鹬蚌相争而渔翁得利

burn the candle at both ends make both ends meet play off one against the other headless rivet with both ends socket shank the ends of the earth play off one against another middle-of-the-roader in the middle middle-of-the-road middle-of-the road bang in the middle pressure against the ends difference between both ends beam supported at both ends beam supported of both ends rod threaded at both ends manage to make both ends meet beam with both ends built-in all working time saved both ends ends of the earth