We have a room behind the double-car garage. This serves as a garden room and equipment storage area (wood chipper, lawn mower, etc.). The opening is wide enough to allow mt DR wood chipper to be pulled through, but it did not allow us to close off the area in the winter to conserve heat for the plants wintered over. My solution was to build a simple double barn door separating two areas.
The double barn doors are pine boards that were edge-glued with biscuits into solid panels. The back side has three boards running along the back to keep the panel flat. The front side is trimmed with pine boards to cover the side edge that closes the gap between the door and the wall. Due to clearance issues, no door rollers were installed, but it does not affect the doors.
The doors were painted to provide some contrast to the garage walls, and the door hardware is simple door pulls. The doors are held together with edge strips that have ceramic magnets (set in pockets) to prevent the doors from drifting apart.