Disclosed is an improved composite substrate for use in a magnetic recording-and-reproducing
device. It comprises an "L"-shaped main plate and a separate sub-plate. The "L"-shaped
main plate has a major section of relatively large area and a minor section of
relatively small area, integrally connected to one side of the major section. The
sub-plate has a square or rectangular piece cut and separated from the minor section
of the main plate. When being inversely arranged and jointed together two composite
substrates can define a square or rectangular shape.
