I have a cake order that calls for 2 12X18 cakes put together side by side which will make it a 24X36. My question is.....Is there anything in particular that I have to do when I put them together? So that, for example, the line that divides the 2 cakes won't show. Or is there anything else that I have to do to put them together before I start frosting? 
OMG!! I've never seen a cake that big!! I've done 2 11X15s before and they barely fit in the "sheet cake" box. What will you put it on?
When doing 2 cakes side by side to make one cake, I just butt them up as close together as possible and ice it as usual. You have to make sure you have a board sturdy enough to hold them. If your board has any give in it, the icing will crack down the middle.
Be sure they are the same hieght and use buttercream to stick them together. Once they are together frost like you normally would. I did this not to long ago and did not have any problem. One half was chocolate the other lemon. Hope this helps.
OMG!! I've never seen a cake that big!! I've done 2 11X15s before and they barely fit in the "sheet cake" box. What will you put it on?
When doing 2 cakes side by side to make one cake, I just butt them up as close together as possible and ice it as usual. You have to make sure you have a board sturdy enough to hold them. If your board has any give in it, the icing will crack down the middle.
This is the biggest thing to consider - I would get a sheet of MDF (particle board) cut to size. I doubt you can find one at a cake store that big. ALSO, be sure you have room in your vehicle to transport it!!!
What do they want on top for such a HUGE cake? Holy smokes!
Melissa
Normally when I do this with any sized cake, I trim just a little bit of the "done-ness" off the edges that butt together to give the center a tighter flawless fit. I also smack them together with buttercream and then smoosh it together tightly and take a piping bag with just a coupler in place and pipe like I would for a dam for fillings, and fill that gap up really good just to be sure it doesn't settle and become a mote lol.
Also I use very thick plywood... hubby is a Carpenter and is always bringing home scrap wood that we clean up and cover with clear contact paper that way nothing ever touches the board itself, and then I'll cover that with fancy foil or wrapping paper or whatever and if it's wrapping paper and isn't food safe I'll cover again with clear contact paper just enough that it's just covered and leaves a gap on the back between the permanate paper that covers the board and the top paper that will be coming back off. 
Hope that makes sense...
I have a cake order that calls for 2 12X18 cakes put together side by side which will make it a 24X36. My question is.....Is there anything in particular that I have to do when I put them together? So that, for example, the line that divides the 2 cakes won't show. Or is there anything else that I have to do to put them together before I start frosting?
Thank you all for your help! I now feel pretty much at ease about making this cake. Thank you, thank you, thank you 
Putting those cakes side by side won't result in a 24x36.
You'll either end up with a 12X36 or you'll end up with an 18x24. You're either doubling one side or the other - not both.
To get a 24x36, you'll have to use 4 cakes.
LOL good catch - of course! FOUR 12x18s HOLY SMOKE!!!!
Melissa
Is your order for a 24 X 36 cake or just two 12 X 18's side by side?
I ask because two 12 x 18 cakes side by side with the 18" sides together would only be an 18 X 24 cake.
If you put the 12" sides together it would be 12 X 36.
If you need a 24 X 36 cake, that would actually be four 12 X 18's - yikes!
I only use 2 mixes for a 12x18 but I add pudding to it too....but anyhow.....the sheet cake in my photos is two 12x18's side by side......and I just used one sheet of foam core board and frosted the two edges that were going to be pushed together and it was fine.....I had no issues with delivering it.....it didn't crack or even begin to separate you couldn't tell they were two different cakes at all!!
thank god someone besides me is good at math
Jen
hehe. I think it's more of an attention to detail thing more than a math thing. Usually, I'm the one to point out math mistakes. I guess I'm trying to read these too fast. 
(note to self....slow down!!)
I have made a cake that was 6 - 12 x 18 cakes put together. It was 24 x 54. I was afraid of not having a sturdy enough board so I had the construction company I was making the cake for, cut me a enormous piece of wood. To make the seam invisible I just kept applying icing till I couldn't see it anymore after using my Viva. Good luck!
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=85703
Putting those cakes side by side won't result in a 24x36.
You'll either end up with a 12X36 or you'll end up with an 18x24. You're either doubling one side or the other - not both.
To get a 24x36, you'll have to use 4 cakes.
It is a 24X36 they want. So it is 4 cakes........sorry! It is for a huge military retirement........
For that large of a cake, I would have a piece of wood cut to size for you. That's gonna be a heavy cake!!
Please post pics when you're done so we can marvel at it!
I will definitely post pics! I am taking your advice on the piece of wood. My husband will be taking care of that part for me
The cake will be cut into the shape of Sergeant Major chevron for the Marine Corps. The whole cake will be the chevron. I also can't wait to see the finish project. Thanks again!
Denise
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