  An algebraic framework for quantization in presence of arbitrary number of
point-like defects on the line is developed. We consider a scalar field which
interacts with the defects and freely propagates away of them. As an
application we compute the Casimir force both at zero and finite temperature.
We derive also the charge density in the Gibbs state of a complex scalar field
with defects. The example of two delta-defects is treated in detail.
