pumping water into the collapsible hoses 165 265 and 166 266 overcomes the bias of the spring steel causing the rollable door 150 250 to unroll and move the roller 140 240 in a downwards direction across the doorway 120 220 as the rollable door 150 250 is unrolled from roller 140 240 the magnetic strips 155 255 and 156 256 mounted on the rollable door 150 250 are attracted to and make an air tight seal with the magnetic strips 135 235 and 136 236 mounted on the flexible shelter wall 110 210 the hydraulic pressure in the collapsible hoses can be maintained by means of a valve not shown in the hydraulic system this means that the pump does not have to operate continuously once the door is closed the valve is opened thereby releasing the hydraulic pressure when the door is about to be opened when the pumping station 160 260 pumps water out of the collapsible hoses 165 265 and 166 266 the bias of the spring steel causes the rollable door 150 250 to roll up around the roller 140 240 thereby separating the magnetic strips 135 136 or 235 236 and corresponding magnetic strips 155 156 or 255 256 from one another breaking the magnetic seals as it does so and moving the roller 140 240 to its raised position adjacent the top side 112 212 of the doorway 120 220 thereby opening the doorway 120 220 when the doorway 120 220 is closed.