釋氏要覽 3.114

3.114

此坐禪資具也。經云。用韋為之（熟皮曰韋）廣一尺。長八尺。頭有鉤。從後轉向前。拘兩膝令不動。故為乍習坐禪易倦。用此檢身助力故。名善助。用罷屏處藏之。

This is a tool for sitting in meditation. The sūtra states: 'It is made of tanned leather (cured leather is called wei), one foot wide and eight feet long, with a hook at the end. Passing from the back around to the front, it binds both knees to keep them immovable. Because beginners practicing seated meditation easily fatigue, this is used to restrain the body and assist its strength; thus it is called a good support. When finished using it, hide it away in a concealed place.'