Picture frames, if modified correctly, can protect paintings from damage when they are in transit. At the Tate Gallery (London), the modifications involve the incorporation of a dust-sealed and adequately rigid sheet of Perspex at the front and a similarly sealed sheet of board at the back, and the use of a hanging fixture which is firmly attached to the main body of the frame. (Specific instructions on where fixtures should be placed on specific sizes of frames are provided.) Paintings without frames must be provided with storage frames which then double as travel frames.