I usually write w/ buttercream on my cake boards/drums and I want to apply letters to it instead. How do I get them to stick?

Try a bit of thinned or warmed up piping gel. Works for me.

I use a paintbrush and a tiny amount of corn syrup on the back of fondant or gumpaste letters. I have it on hand and I feel it is the easiest. I have also used royal icing, chocolate, and occasionally, water.

HTH

I thought of piping gel too, but I'm out. I have corn syrup! Yay! Maybe I'll try that! Thank you both!

I use tylose that's been mix into boiling water and then sits for a few days....great glue.

Great idea, but I'm doing the cake now and I don't have a few days to make the "glue"....I'll remember it for next time though!! Thanks!