Hold Open. The Alpro Heavy Duty Transom Door Closer is designed to be concealed within the transom header bar of the door. It is suitable for use with single or double action aluminium single or double doors. The heavy duty closer has a built in positive back stop with adjustable spring strength, dual closing speed and optional 90˚ hold open facility. It is supplied complete with required fixings and fitting instructions. . Heavy duty door closer. Designed to be concealed within the transom header bar of the door. Dual closing speed. Adjustable spring strength