A roll-up type industrial door including a flexible sheet or woven fabric forming a curtain for closing a door way having an upper end, a lower end and two opposite side edges. The sheet has a main area and elongate side edge sections that are thicker than the main area. A shoulder is formed where each side edge section meets the main area. A curtain winding mechanism is connected to the upper end of the curtain and is used to raise the curtain. A pair of spaced apart guide channels are also provided and the side edge sections are movable therein. Each guide has one or two elastic members which act as locking blades. The locking blades of each guide form an elongate slot that receives a side edge section of the curtain.