cheers guys.. I will try to take some pics soon

basic question I guess but not one I have managed to find a satisfactory answer to....

Hiwin rails and bearing block fitting (and hopefully removal)

I need to trial fit some of the carriage parts to check a couple of things work as we want.... so I need to temporary fit the rails & bearings. Reading the manual it seems the rails must be horizontal when i fit the bearings... ie bolt holes up, slide on using the plastic packing piece as a guide and I assume ball bearing keeper?

Is this the only way to do it?
can I remove the bearings using the reverse ie sliding off the rail onto the plastic packing piece?

are the balls free to fall out if I get it wrong?

thanks