  In order to get a significant Zeeman signature in the polarised spectra of a
magnetic star, we usually 'add' the contributions of numerous spectral lines;
the ultimate goal is to recover the spectropolarimetric prints of the magnetic
field in these line additions. Here we want to clarify the meaning of these
techniques of line addition; in particular, we try to interpret the meaning of
the 'pseudo-line' formed during this process and to find out why and how its
Zeeman signature is still meaningful. We create a synthetic case of lines
addition and apply well tested standard solar methods routinely used in the
research on magnetism in our nearest star. The results are convincing and the
Zeeman signatures well detected; Solar methods are found to be quite efficient
also for stellar observations. The Zeeman signatures are unequivocally detected
in this multiline approach. We may anticipate the outcome magnetic fields to be
reliable well beyond the weak-field approximation. Linear polarisation in the
spectra of solar type stars can be detected when the spectral resolution is
sufficiently high.
