a power tool such as a portable electric drill turns gear 323 and sleeve 316 as shown in fig1 gear box 308 is attached to a fixed part of the door structure and spring 302 is placed on shaft 301 in its normal closed position end cones 303 and 306 have been threaded into opposite ends of springs 302 before they are assembled about shaft 301 shaft 301 is moved through sleeve 316 opposite ends of the shaft 301 are attached to drums such as drums 33 and 34 accommodating cables which are attached to bottom portions of the roll up door the block 318 is turned to move it toward the end of the threaded section 317 b of sleeve 316 as shown in fig1 and 13 end cone 306 is attached with bolts 319 to block 318 spring 302 in its normal non tension condition extends along shaft 301 end cone 303 is anchored to shaft 301 with set screws 304 to fix the position of end cone 303 on shaft 301 stop collar 321 is positioned a selected distance from block 318 and anchored to sleeve 316 with set screws 322 spring 302 increases in length by a distance equal to the diameter of the spring coil or wire for each 360 degree turn of the spring the spacing between block 318 and stop collar is determined by the diameter of the coil and the desired number of turns of the spring a power tool such as a portable electric drill connected to a socket is used to.