Let us see what is panel. Panel is a a rectangular piece of wood. Hence a single panel door consists of one rectangular piece only which is fitted to the wall. Double panel door is one consisting of two panels, one on the right another on left.
As you have searched Google, it is no use giving link. Google images for single panel and double panel doors can also be seen.
This is actually a matter concerning Engineering. I hop some of our members specializing in civil engineering will explain better.
G. K. Ajmani Tax consultant http://gkajmani-mystraythoughts.blogspot.com/
To add to the reply given above I think single panel doors are non-sliding while the double panel doors are basically sliding ones....
Panel and sliding are two different things. A single panel door will have one bigger panel but the double panel will have two panels each approximately half the size. In Delhi metro train, the doors are sliding and double. In lifts also, the doors are double panel and sliding. The cars have single panel non sliding doors.
One needs some expertise in civil engineering or construction techniques to understand these concepts. I hope that some members with expertise in this field would explain better.
G. K. Ajmani Tax consultant http://gkajmani-mystraythoughts.blogspot.com/
