Locking securement for sheet metal housing cover

Claim 1

IN A HOUSING HAVING A BODY AND A COVER WITH OVERLYING MARGINAL WALL PORTIONS WHICH MOVE EDGEWISE IN OPPOSITE DIRECTIONS DURING DISPLACEMENT OF THE COVER, ONE OF SAID MARGINAL WALL PORTIONS HAVING AN EDGE THAT EXTENDS TRANSVERSELY TO SAID DIRECTIONS AND IS EXPOSED ON THE EXTERIOR OF THE HOUSING WHEN THE COVER IS IN ITS CLOSED POSITION, MEANS FOR SECURING THE COVER IN ITS CLOSED POSITION IN A MANNER SUCH THAT ONLY AN AUTHORIZED PERSON CAN EFFECT EXPEDITIOUS DISPLACEMENT THEREOF, SAID MEANS COMPRISING: (A) A KEYHOLE-SHAPED SLOT IN SAID IDENTIFIED MARGINAL WALL PORTION HAVING ITS MOUTH OPENING TO SAID EXPOSED EDGE AND ITS LARGE INNER PORTION SPACED FROM SAID EDGE; (B) MEANS ON THE OTHER MARGINAL WALL PORTION PROVIDING A THREADED BORE WHICH OPENS TO BOTH SURFACES OF SAID WALL PORTION AND WHICH REGISTERS WITH THE LARGER INNER PORTION OF SAID SLOT WHEN THE COVER IS IN ITS CLOSED POSITION, THE DIAMETER OF SAID BORE BEING NO GREATER THAN THE WIDTH OF THE MOUTH OF THE SLOT; AND (C) A SCREW HAVING (1) A SHANK PORTION THERADEDLY RECEIVED IN SAID BORE, (2) A HEAD AT ONE END OF THE SHANK PORTION, LARGER THAN THE LARGE INNER END PORTION OF THE SLOT, (3) A SUBSTANTIALLY CYLINDRICAL SHOULDER AT THE UNDERSIDE OF THE HEAD AND BY WHICH THE HEAD IS JOINED TO THE SHANK PORTION, SAID SHOULDER HAVING A DIAMETER TO BE SNUGLY RECEIVABLE IN THE LARGER INNER END PORTION OF THE SLOT AND THUS HOLD THE OVERLYING WALL PORTIONS AGAINST EDGEWISE SEPARATION WHILE THE HEAD HOLDS SAID WALL PORTIONS IN FLATWISE ENGAGEMENT UPON TIGHTENING OF THE SCREW, AND (4) A POLYGONAL OUTWARDLY OPENING SOCKET IN THE HEAD, AND A COAXIAL PRONG PROJECTING OUTWARDLY FROM THE BOTTOM OF THE SOCKET SO THAT TURNING THE SCREW TO THE POINT WHERE THE SHOULDER IS DISENGAGED FROM SAID SLOT REQUIRIES THE USE OF AN ALLEN HEAD TYPE WRENCH HAVING A COAXIAL WELL THEREIN TO ACCOMMODATE SAID PRONG.