SE 90° Hold Open. The dormakaba (formerly known as Dorma) RTS 85 transom concealed door closer offers a solution for installations where door control must be provided without disturbing the aesthetic appearance of the door. A complete line of accessories is available to accommodate virtually any door and frame configuration.. Door closer concealed in the door frame. For single and double action doors. Fully controlled closing with adjustable speed. One closer body for all types of fixing