The end of a three foot rail section with the "NOTS coupler" called because although we were encouraged to keep the price down by using off the shelf parts, this item is " Not Off The Shelf ".  The coupler is 12" long and sticks out 6" and into the next section.

The other end of the three foot rail section with an end coupler.  This is where the end cap attaches.  It is essentially a "NOTS Coupler" cut in half.  It can be changed out with a full coupler to extend the track in  additional 3 foot increments. 

The end cap is 25" wide and attaches to the end of each rail.  There is a bubble level in the center of each one for easy leveling.  The end cap attaches one inch higher that the track itself to help prevent an accidental roll off.