A Saint Andrew's cross is a piece of BDSM furniture made up of a cross set diagonally in the shape of an X. It restrains the subject in a standing spread-eagled position. The St. Andrew's cross was most recently brought to public attention when it was used by Christian Grey to restrain Anastasia Steele in "Fifty Shades of Grey."
In a BDSM context, the Saint Andrew's cross is a popular piece of dungeon furniture. The subject is tied at his or her wrists, ankles and sometimes waist, either facing the front or the back. When facing the front, the subject can be teased, while the back-facing position is more often used for impact play like whipping, flogging or spanking. The crosses are often padded with leather or vinyl to make long-term use more comfortable.
A Saint Andrew's cross is also known as an X-cross, diagonal cross, saltire cross, X-frame, BDSM cross bondage cross or kink cross.