As you plan out your indoor growing equipment, there are just two things to say here.
First, make sure you see the green arrow on the one rail half and have the direction of that arrow slide into the other rail half. Easy, huh?
The second thing to mention is that you need to line everything up well. Each rail half is one meter ( 3’3″) so when assembled, you are now at 2 meters (6’6″).
Note: The extruded aluminum rail can be easily cut for fitting more exactly into limited grow setup spaces, or you can always use just half a rail.