How would you say that Billy is sneaky but not using it as a character trait?

I'm doing a book report and Where the Red Fern Grows, and i have to explain what different symbols mean to the book, and what the author wanted us to know about the symbol and its meaning, and i am stuck on describing a mask. i know that billy is sneaky, but i don't know how to say that he is sneaky without using it as a character trait. If you are confused, i will give examples of other symbols that i did. For example: another symbol i did was a tin can. Well, most of you probably already read the book, so you should all know that Billy saved up for 2 years to buy his 2 coon hounds. So, (2 years is a long perios of time to save up) i said that the tin can stands for persistance. Why? because if you aren't persistant with your work, then you will not get far. (i.e. if you have a dream/goal, you have to work hard and never give up and you will eventually succeed. Please help ASAP! This project is due tomorrow!

Thank ya! :)