If not, what do you do?

I've never used one becuase primarily I never wanted to put a big 'ole hole in the middle of my cake. Second, I've never had a need to use one.

I grease-only-no-flour my pans (haven't floured pans in 30 years), use the baking strips and reduce the oven temp to 325 (in a regular home oven .... might need adjsted for convection or comm'l ovens).

Here's a thread where I explain the science behind how baking strips work: http://cakecentral.com/cake-decorating-ftopicp-6626888.html#6626888

..moving to Decorating forum.

Everything you need to know to make, decorate and assemble tiered/stacked/layer cakes:

http://www.cakecentral.com/cake-decorating-ftopict-605188.html

Relax, get a glass/cup of your favorite beverage because this a long read.

HTH

The biggest layer I've done is a 16" square and I didn't use a heating core. What I did use was baking strips to keep the outside from baking before the center did.

no no no... to the baking core...

I use a flower nail inverted upside down that works just fine for me. The largest I have baked is a 14 inch (not very big) or I also use it with a 1/2 sheet cake (11 x 15) and it works great for me...

I bought one and I've never used it. I just reduce the oven temp and it's always worked out fine.

Haven't used a heating core - ever - in 40 years of baking. It's just a stupid Wilton toy that W thought up to sell you something you don't need.

I don't own one either. I have used an upside down flower nail but honestly I don't notice a difference when I forget to use it.

I too bake at a lower oven temp for layers over 10".

Nope. Like the others, 325 with bake even strips. I have used the flower nails in 16" pans, but they left behind a gray mark on the cake