Add a Wheel
Attach a 5" castor to the bottom of the swinging edge of the wall so that it will be concealed when the wall is closed. Position the caster so that the wheel extends lower than the door frame but doesn't quite touch the floor; if the door settles due to heavy storage on the other side, the caster will keep it from scraping.
Note: These homeowners used the swing-out door to conceal hunting equipment — including firearms. Always make sure any firearms are safely secured and out of the reach of children.