Support for a 4 tier cake

I made a pillow cake that had several layers and the cake pieces where heavy I didn't really know how to support these layers one on top of the other. I would like to learn the ins and out of supporting a cake.with all the weight ..Or maybe my cakes are made to heavy, I need some advise on this subject

Thanks for the support ladies.Yes this was the cake in my gallery that my client said it clasped but I did put dowels to support all layers.I just wanted to make sure because this cake was heavy that it wouldn't do that,before I left her mother had mention that the cake looked like it was going to fall and I told her that it wouldn't fall if no one touches the cake I assembled the cake at the hall.Come to find out there were three sides to the story.I called the place where they had the event and the lady that worked there said that the cake was moved to a higher cake display plate and that two hours to the event the top piece fell down and they tried to put it back together and couldn't do so.My client said it was just moved from one side to another and that it wasn't moved to any cake plate stand my thing is this am I responsible for the cake falling when I told her mother not to move the cake? my client wanted me to give her back 1/.2 the money. I told her no I put a lot of work and effort to that cake and I charged her a very cheap price.How dose one go about being responsible for what as far as when you make a cake for someone and deliver it. Should I draw up a contract because after I left I don't know what happened there. My picture shows right when I left how the cake was fine.Since am new at this it bothered me so much to feel I may have been responsible that the cake fell.