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Wings of the Bulwark (干城の翼 Kanjō no Tsubasa?) is the 1st chapter of the 13th volume and the 45th chapter overall of the Attack on Titan: Before the Fall manga, written by Ryō Suzukaze and illustrated by Satoshi Shiki.
After seeing the vertical maneuvering equipment, the final version of the device, Kuklo goes to test it in the forest. After learning how the device works, he performs a test run and marvels how it is much easier to operate. Impressed as well, both Jorge and Carlo inquire if it is possible to mass-produce it for all members of the Survey Corps; however, Sharle notifies them that she went to Gloria Bernhart of the Military Police and requested that the device be allowed to be properly tested. Gloria agrees but demands proof that it can defeat a Titan; otherwise, the Survey Corps will be permanently disbanded!
Kuklo goes and puts on the newest version of the device. Noting how it feels more natural with both arms holding triggers, he questions if it requires both hands to use. Angel directs him to take the handles and touch them to the cases on his hips; hearing a click, he pulls the handles out and sees each one now possesses a flexible blade. Everyone present marvels at the new design and shape of the sword, but Kuklo asks why the sword is so much lighter. Angel states the sword, while looking flimsy, is actually much stronger than it appears to be and to not be fooled by it. Hearing it got both Angel and Xenophon's seal of approval, Kuklo changes his mind and expresses his eagerness to test the vertical maneuvering equipment out.
After traveling to a nearby forest, Kuklo is ready to begin testing the equipment out; Angel tells him that he must control the ports with moving his body in order to activate the anchors. Kuklo launches the anchors and takes off; caught by surprise initially by the speed, he slowly begins to take control and starts committing the different movements to memory. On the ground, Angel regrets that he cannot see it in action for himself, but Carlo tells him it looks incredible and that he had no idea such feats were possible. Carlo looks to Jorge and asks for his opinion, but stops when he sees his father silently crying tears of joy.
Angel again admits that while brilliant, he lacked the foresight to take into account that Titans were mobile targets. While he had it mapped out in his head, Xenophon had trouble visualizing it himself until reading Cardina's report that came in. With both inventors finally on the same page, they crafted the vertical maneuvering equipment from the ground up. He also goes on to say that in Cardina's report, his noted that the sword accompanying the old device broke after several slashes; to counter this, the boxes on the sides contain backup blades that can be replenished.
Kuklo finally lands and lauds how the equipment is incredible and easier to use than previous iterations. Angel smiles and merely states that the user is what makes it incredible. He goes on to say that Sharle's involvement is just as equal as Kuklo and Cardina, explaining that Sharle ventured alone to find him in the Underground City, surprising everyone and embarrassing her. Angel continues and reveals that she provided the missing piece by combining both the control grip and the sword itself into one; he admits that without Sharle, there would be no vertical maneuvering equipment.
Carlo asks if Angel can mass produce the equipment for the soldiers as well as backups in reserve. It is revealed that Gloria Bernhart, and the central Military Police headquarters, were discreetly informed of the creation of the equipment and agreed to the mass production. Jorge is slightly disappointed that the Military Police is already aware of the equipment's existence. Sharle reveals that in two months, an expedition will be sent out to bring back proof that a Titan can be defeated with the equipment. If it fails, the Survey Corps will be permanently disbanded at the expedition's conclusion.