Be aware that panel frames just slip over edge of glass, may be bonded poorly or not at all. Screws in frame corners are the only things holding it together. Lifted by top edge, they try to spring off glass.
If you handle panels in portrait orientation, you can grab by left and right edges, holding them together when lifting.
Once laid on rails (will try to slide off roof), and clamped to rails, that holds frames together.
It can be useful to bolt a stop at bottom of rails (if oriented vertically) to support bottom edge of panel.
For horizontal rails, either need a support below rails to block panel from sliding, or put bolts and nuts through holes in panel frames so they hook on rails.