  A virtual knot, which is one of generalizations of knots in $\mathbb{R}^{3}$
(or $S^{3}$), is, roughly speaking, an embedded circle in thickened surface
$S_{g} \times I$. In this talk we will discuss about knots in 3 dimensional
$S_{g} \times S^{1}$. We introduce basic notions for knots in $S_{g} \times
S^{1}$, for example, diagrams, moves for diagrams and so on. For knots in
$S_{g} \times S^{1}$ technically we lose over/under information, but we will
have information how many times the knot rotates along $S^{1}$. We will discuss
the geometric meaning of the rotating information and how to construct
invariants by using the "rotating" information.
