“敲门砖”英语怎么说？

“敲门砖”，字面意思指“拣来敲门、门开后即被丢弃的砖头（brick picked up to knock on the door and thrown away when it has served its purpose）”。常用来比喻世人借以猎取功名的工具（thing used as a means for fame and position），一达目的...