I wanted to know how to pronounce the superscript # symbol in the following sentence and whether it has a specific meaning when applied to T:
"With these labels, each motion $ T: X \rightarrow X $ of the square sends each vertex to a vertex, so determines a permutation $ ^\# T: Y \rightarrow Y $ of the set Y of vertices."
It's from Mathematics Form & Function Chapter 1 part 7. (page 21 in my copy).