  A method to measure the electrical connectivity between square
superconducting plates joined by weak link interfaces is presented. It is based
on observation of lines where the flow of critical current abruptly changes
direction due to the presence of weak links, and the confinement created by the
shape of the sample. The method is demonstrated using magneto-optical imaging
(MOI) of systems consisting of up to 2 X 2 plates joined to form a larger
square. Common features are found in the current flow patterns, which allow to
measure the electrical connectivity between the plates by observing an angle
between pairs of lines indicating where the current abruptly changes flow
direction, so-called discontinuity, or d-lines. The samples used in this study
are Nb films with weak links created by focused ion beam machining.
