I am making a baby rump cake tonight for a shower this weekend. When I make the baby rump, do I asemble the it before or after I put it on the cake? Also, do I put supports under the rump? TIA

Hi, I haven't personally made one but there is an article in the article section on CC under Baby Shower that should help you.

http://cakecentral.com/articles/426/baby-shower-how-to-make-a-baby-rump-cake

I've made 2 baby rump cakes (I assume you mean the diaper bottom & legs cake)...2nd one turned out much better b/c I learned from the first. I made my bottom from the "dome" pan so the shape is easy. Made the legs from RCTs and molded them with wax paper (used bottom to get an idea for size & positioning). Then had a bottom cake that was larger than the dome pan so the whole baby bum sits on top of something. I put the dome cake on it's own board & dowelled the lower cake to support this. Covered lower cake in bc and fondant first. Then stacked bum part and used white fondant to make the diaper being sure to leave space at the legs to ruffle the edges. I covered the legs (RCT) with 2 layers of fondant (my mistake the first time was only using 1 layer - and you could see rice crispies underneath making the baby look like he/she had horrific cellulite)...used skewers to support legs and have them sit where I wanted them to. Covered the unfinished edge of "diaper" with a baby blanket of fondant.

Hope this helps and good luck!

thank you both for your help. I will let you know how mine turns out.