FIG.  1 shows a perspective view of a typical computer 100 where a top cover (not shown) of a chassis 101 is removed.  As can be seen in FIG.  1, various kinds of electronic parts 102 are disposed on a main board 103 of the computer 100.  The main board 103 is disposed on a bottom surface of the chassis 101 via supports 105. 
FIG.  2 shows a perspective view of the computer 100 in FIG.  1 where a mezzanine board 201 is installed.  For example, the mezzanine board 201 is fixed to the side surface of the chassis 101 by screws or adhesives.  In order to properly mount the mezzanine board 201, the position of the mezzanine board 201 must be aligned relative to the main board 103 such that connectors on the mezzanine board 201 mate with connectors on the main board 103.