  We present a multi-epoch X-ray spectroscopy analysis of the nearby
narrow-line Seyfert I galaxy NGC 5506. For the first time, spectra taken by
Chandra, XMM-Newton, Suzaku, and NuSTAR - covering the 2000-2014 time span -
are analyzed simultaneously, using state-of-the-art models to describe
reprocessing of the primary continuum by optical thick matter in the AGN
environment. The main goal of our study is determining the spin of the
supermassive black hole (SMBH). The nuclear X-ray spectrum is photoelectrically
absorbed by matter with column density $\simeq 3 \times 10^{22}$ cm$^{-2}$. A
soft excess is present at energies lower than the photoelectric cut-off. Both
photo-ionized and collisionally ionized components are required to fit it. This
component is constant over the time-scales probed by our data. The spectrum at
energies higher than 2 keV is variable. We propose that its evolution could be
driven by flux-dependent changes in the geometry of the innermost regions of
the accretion disk. The black hole spin in NGC 5506 is constrained to be
0.93$\pm _{ 0.04 }^{0.04}$ at 90% confidence level for one interesting
parameter.
