A-Frame is a large triangular frame with horizontal steel bars crossing the inside of the frame (some versions have a lattice of ropework instead of the bars). A person can be tied to the A-Frame in various positions, but usually, they will have their hands tied to the top of the frame with their legs spread apart and tied to the bottom. The bound person can be tied with their face to the frame or with their backs to it, depending on the type of torture the dom has in mind. The shape of the A-Frame and variety of bondage options means that there are positions that don’t put much stress on the body, allowing linger periods of bondage.
A frame can be found in dungeons.