The gate is supported by two (counterbalance) posts.
The "gate proper" should be equal to the opening plus 6"
The "counterbalance" should be equal to 50% (minimum) of the gate proper.
The important element of the "counterbalance" is not weight, but length.
Pickets are not necessary on counterbalance portion, unless required by design.
Make sure you refer to UL325 for safety elements in design.
Gate must be properly braced (or trussed)
If the gate is square tubing, top rail must be 2" X 2".
If the gate is round pipe, top rail must be 2 1/2 O.D. square tube or 4" O.D. round fence pipe.
E/Z Slide Track mounts to top rail of the gate and counterbalance (i.e. overall length)
If top rail is steel IGD mounting brackets are provided; if aluminum either mounting brackets can be used or stitch welding.
Trucks (trolleys) are mounted to counterbalance posts.
Trucks run inside the E/Z Slide Track. The trucks do not move, they are fixed.
The track and attached gate slide on the trucks.
Lower guides are provided to keep gate plumb.