A common misconception is that closet door hardware, especially hardware for sliding closet doors, require a bottom track.  The belief is that the bottom track helps support the weight of the doors as well as keep the doors aligned.

The Johnson Hardware we supply with our closet doors is actually designed to support the entire weight of the doors at the top.  The rollers are all sets of 3 or 4 wheels that have been machine turned and balanced. This means that the optional bottom track is used only to help guide your sliding closet doors and bifold doors.

When should I use a bottom track?

You really only need to use the bottom guide when there is a concern that the doors might be bumped hard enough to swing back and forth.  Some good examples would be if the doors are being be used between rooms or if you have small children or large pets.

Are bottom tracks only for sliding closet doors?

No.  Larger bi-fold doors are also good candidates for a bottom guide track.  Follow the same rule as with your sliding closet doors.  If you think your bi-fold doors are going to be bumped a lot then a bottom guide track might be helpful.

Do I need to cut into my floor to install the bottom track?

No.  Since the bottom guide tracks do not support any weight they can be surface mounted to your floor.  Wood strips can be placed on either side of the track to give the look of a finished threshold.  If you have not installed your floor you can also use a bottom guide track.  In this case you would simply install your flooring on either side of the bottom guide track.  The nice thing about this method is that the track is submerged below the floor level so there is no concern about tripping.

So while a bottom track is not needed to support the weight or your doors, it can help to guide your doors.