The Waki-Biki (Japanese: 脇引 or 腋引), also known as Waki-Date, are part of the Japanese Samurai armor (Yoroi).
Waki-Biki are armor pieces used to protect the armpits. They are usually square or rectangular in shape, with a U-shaped upper area. They are attached to the breastplate with silk cords. Waki-Biki are typically made of steel. The armor may be in the form of plate, chain, or scale armor.
The individual parts of the plates are flexibly connected to each other with silk cords. Another version, also referred to as Waki-Biki, is a type of jacket or vest, also equipped with the different types of armor, and is worn under the breastplate (Do). A third version is a plate that is attached to the opening side of the breastplate to make it more difficult for an opponent to open the armor.