The J-Tool is a tool that can be used to bypass the locking mechanism of double doors.

We found this tool via a video from LockpickingLawyer and had to add it to our collection. For a full demonstration of this tool, watch the video:

You can insert the tool into the gap between the two doors. After inserting the tool, you can place the headpiece on the dial of the double door. Once inserted, you should be able to turn the black lever of the J-tool to rotate the head of the tool. This unlocks the door lock.