how do I use the letters in the corners by themselfs

Eunice_Artis

how do I use the corner letters? In a game level there are lone letters in the bubble levels and I don't know how to use them and with that in mind I can not complete the level. There are bubbles in the corner letters and I need them to complete the level.

Sandra_Snead

You need to use a blaster or a crown to clear the bubble.