  We define and study a gluing procedure for Bridgeland stability conditions in
the situation when a triangulated category has a semiorthogonal decomposition.
As an application we construct stability conditions on the derived categories
of ${\mathbb{Z}}_2$-equivariant sheaves associated with ramified double
coverings of ${\mathbb{P}}^3$. Also, we study the stability space for the
derived category of ${\mathbb{Z}}_2$-equivariant coherent sheaves on a smooth
curve $X$, associated with a degree 2 map $X\to Y$, where $Y$ is another smooth
curve. In the case when the genus of $Y$ is $\geq 1$ we give a complete
description of the stability space.
