This is not a step by step how to but the premise and the design is dirt simple. If you're handy, you should be able to emulate this no problem. Also, I keep calling the U-channel post a T-post throughout the video; jut ignore that.

You'll need a power drill (with a set of drill bits and a drive bit) and a hacksaw for tools. You'll need a U-channel-post 2.5 times the width of your doorway, two garage door pulleys, about 24" of 1/8"x2" steel bar stock, a box of exterior wood screws, eight 3/8" washers, four 3/8" nuts, and four 3/8" hex bolts, two at least 2" long and two at least 1" long. Also a door. If you don't have a door, you can easily build one from a couple 2"x4"s and a sheet of 3/4" plywood.

Mount the U-post level on the wall above the doorway. Place the halfway point of the U-post on one edge of the doorway that you want the door to roll towards. Use an excess of wood screws if mounting to wood, a few bolts in mounting to heavy steel, or a good number of masonry screws if mounting to block. Make sure you leave 3-1/2" of clearance above the U-post and, if you want to totally seal the doorway, make sure the bottom of the U-post is at least an inch above the top of the doorway.

Now cut the steel bar in half with the hacksaw. Drill a 3/8" hole at a center point 3/4" to 1" from the top edge. Use multiple drill bits and work your way up to 3/8" and make sure to lube the bit with some cutting oil or motor oil. Now drill two or more 1/8" mounting holes on the opposite end of the bar where you want this bracket to mount to the door. Now bolt a pulley to each bracket through the 3/8" hole, use washers to space it further from the bar as needed. Now screw the brackets to the door, with the pulley facing inward and make sure the pulleys are an equal height from the top of the door.

Now hang the door. Position the door where you want it to rest on the doorway. Now clamp one of the small bolts, with washers, over the top of the U-post next to a pulley to create a forward stop. Now position the door where you want it to stop at and do the same on the opposite end. That's all there is to it! Enjoy.