  Geometry of the spacetime with a spherical shell embedded in it is studied in
two coordinate systems - in Kodama-Schwarzschild coordinates and in Gaussian
normal coordinates. We consider transformations between the coordinate systems
as in the 4D spacetime so as at the surface $\S$ swept in the spacetime by the
spherical shell. Extrinsic curvatures of the surface swept by the shell are
calculated in both coordinate systems. Applications to the Israel junction
conditions are discussed.
