Abstract: An upper end of a flexible door or curtain is attached to an overhead support member while a lower portion of the curtain is disposed on and connected to an elongated horizontal tube along its length. A combination electric motor and gear box is connected to a first end of the tube for rotating the tube in a first direction for rolling the curtain onto the tube and raising the curtain and tube combination, or for rotating the tube in a second, opposed direction for unrolling the curtain from the tube and lowering the curtain and tube combination. Attached to the electric motor/gear box combination is a carriage or roller assembly which engages and rides on a generally vertical guide rail or runner during raising and lowering of the curtain. The engaging force between the roller assembly and the guide rail is adjustable to prevent binding of the curtain as it is rolled up onto or removed from the tube.