To understand why the scissor leg sets are stacked on top of each other first keep inmind thatthe longer the scissor leg assembly the higher the lift will go. For example a 4’ long leg set will provide approximately 3’ of lift, a 6’ long leg set will provide approximately 4’ of lift, an 8’ long leg set will provide approximately 5’ of lift etc. Following this ratio/guideline a lift table application that requires 8’ of lift would typically require a 12’ long leg set. Many applications do not have the 12’ of floor space available to install a lift table that will lift a load 8’. The alternative is to stack 2 or more leg sets; this provides a smaller foot print on the floor and achieves the lift required. The short answer= stacking leg sets saves floor space. With stacked leg sets there are stability issues to consider maintaining safety and stability throughout the operating range, please contact Pentalift to discuss your application requirements.