倒扣接头也叫倒扣矛，是用来在钻、修井过程中倒出卡点以上被卡钻柱的专用工具。打捞或倒扣时，若落鱼被卡或倒不开时，可从倒扣接头处退开，取出打捞钻具。

Reversing Sub is also called reversing spear which is a special tool for reversing stuck drill stem above stuck point in drilling and work over operation. When make fishing or reversing, if fallen object is stuck or fail to be released, the tool can released from thread connection of reversing sub to take out fishing tool.