The invention concerns a method for preparing glass from raw materials in powder form in a furnace comprising three side walls, a roof, an upstream pinion and at least one air injector associated with a gas or liquid fuel injector, at least one of said injectors being arranged in said side walls, in said roof or in said upstream pinion. An MD direction Taber stiffness of the substrate is at least 3 mN\xb7m. The line engaging portion includes a first engaging portion normally spaced a distance \u0394 from the line to form a clearance gap in the line releasing position and a second engaging portion bridging the gap a distance equal to at least \u0394 for arresting the line and preventing movement of the line in the line releasing direction. The first and second leg portions point in substantially the same direction so that door opening and closing forces applied to the gripping region substantially avoid creating torque at the mounting region.