Let $L$ be a framed knot in $S^3$. Let $U$ be a closed regular neighborhood of $L$ in $S^3$.
How can I interpretate the following sentence?
"We identify $U$ with $S^1 \times B^2$ so that $L$ is identified $S^1 \times 0$, where $0$ is the center of $B^2$ and the given framing of $L$ is identified with a constant normal vector field on $S^1 \times 0 \subset S^1 \times B^2$."
I know $U$ is homeomorphic to $S^1 \times B^2$. What confuses me is that framing part.
For example, if framing number is $1$, is the identification the result of one Dehn twist along meridian on $S^1\times B^2$?