This is dependent on the amount of clearance (available wall space) you have on at least one side of your doorway. If you want to be able to access your entire doorway, then it is recommended that you order a hardware kit that is twice as long as the width of your door (for a single door) or twice as long as the combined width of your doors (for double doors). This is to ensure that the door has enough track space to move to when being pushed into the open position. For example, if you are installing a single 4’ door, you will want to order a hardware kit with an 8’ track. If you are mounting two 3’ doors, then you will want to order a 12’ track ((3’ + 3’) x 2 = 12’). If you don’t have the necessary clearance on either side of the doorway for both doors, then you may want to consider one of our Bypass Barn Door Hardware Kits.