BUR #16918 has been approved by @nonamethanks.
create alias behind_back -> holding_behind_back
create alias object_behind_back -> holding_behind_back
The point of both tags are similar according to behind back's Wiki. Meanwhile posts with object behind back shows characters holding an object behind their backs. I will welcome other options or changing this BUR when most of users would disagree with this.
While *_on_back tags refer to objects that are not being held by the character but rests on their back.
You can edit my forum post if there is something wrong.
Updated by Black Metal ist Krieg