Abstract: A mounting structure includes a mounting unit, a plurality of first connectors arrayed on the mounting unit, a plurality of pairs of guide rails attached to the mounting unit, and a plurality of packages having electronic circuit components mounted thereon. Each of the packages has at least one second connector at one edge thereof which is engaged with at least one of the first connectors when the package is inserted into the mounting unit along an associated pair of the guide rails. The mounting structure further includes a rod and a plurality of arms. A first end of each of the arms is attached to the rod so as to be able to pivot or rotate around the rod. A second end of each of the arms is engaged with an edge of one of the packages opposite to the one edge having the at least one second connector when the arms are pivoted or rotated toward the packages, so that the packages inserted in the mounting unit are prevented from coming out of the mounting unit.