Extensible multi-section supporting structures

Claim 1

IN AN EXTENSIBLE SUPPORTEING LADDER, IN COMBINATION, A FIRST, A SUPERIMPOSED SECOND AND A SUPERIMPOSED THIRD LADDER SECTION, EACH SECTION HAVING A FORWARD END AND A REAR END AND SAID THIRD SECTION LOCATED BETWEEN SAID FIRST AND SECOND SECTIONS, EACH OF SAID SECTIONS HAVING TWO SPACED SIDE WALLS AND TRANSVERSELY EXTENDING RUNGS THEREBETWEEN; MEANS FOR SLIDABLY GUIDING SAID FIRST AND THIRD SECTIONS BETWEEN AN EXTENDED POSITION IN WHICH THE REAR ENDS OF SAID FIRST AND THIRD SECTIONS ARE RESPECTIVELY ADJACENT TO THE FORWARD ENDS OF SAID THIRD AND SECOND SECTIONS, AND A RETRACTED POSITION IN WHICH THE FORWARD ENDS OF SAID FIRST AND THIRD SECTIONS ARE RESPECTIVELY ADJACENT TO THE FORWARD ENDS OF SAID THIRD AND SECOND SECTIONS; AND MEANS FOR CONTROLLING THE SEQUENCE OF MOVEMENTS OF SAID FIRST AND THIRD SECTIONS WITH RESPECT TO SAID THIRD AND SECOND SECTIONS, RESPECTIVELY, SAID CONTROLLING MEANS COMPRISING FIRST AND SECOND LOCKING MEANS ROCKABLY MOUNTED AT THE FORWARD END OF SAID THIRD SECTION, FIRST AND SECOND DETENT MEANS RESPECTIVELY MOUNTED AT THE REAR END OF SAID FIRST SECTION AND AT THE FORWARD END OF SAID SECOND SECTION, SAID FIRST DETENT MEANS ENGAGING WITH SAID FIRST LOCKING MEANS WHEN THE FIRST SECTION IS MOVED TO ITS EXTENDED POSITION AND SAID THIRD SECTION IS AT LEAST SLIGHTLY DISPLACED FROM ITS RETRACTED POSITION, AND SAID SECOND DETENT MEANS ENGAGING WITH SAID SECOND LOCKING MEANS WHEN THE THIRD SECTION IS MOVED TO ITS RETRACTED POSITION, AND FIRST AND SECOND CAM MEANS RESPECTIVELY MOUNTED AT THE FORWARD END OF SAID SECOND SECTION AND AT THE REAR END OF SAID FIRST SECTION, SAID FIRST CAM MEANS ROCKING THE FIRST LOCKING MEANS FROM ENGAGEMENT WITH SAID FIRST DETENT MEANS WHEN SAID THIRD SECTION IS MOVED TO ITS RETRACTED POSITION, AND SAID SECOND CAM MEANS ROCKING THE SECOND LOCKING MEANS FROM ENGAGEMENT WITH SAID SECOND DETENT MEANS WHEN THE FIRST SECTION IS MOVED TO ITS EXTENDED POSITION.