Many Alphabet signs often form a radical like K in Kitchen, and M + F in parents to represent Mother + Father. Sometimes we see the main handshape of the letter like the A hand in actor and artist.
Hear are some examples. This is not where you simple fingerspell a word, but rather where the alphabet handshape is adopted within another sign, which movement shift, or sign blend, to form a new meaning that is in someway related to the original letter.
For example in Canberra we are seeing the C blended with City, so in this way both are Radicals within the sign