Slotted bookshelf and book support

Claim 1

IN COMBINATION, A SHELF HAVING MEANS FOR ATTACHMENT TO A FRAMEWORK, AND A COMPRESSOR FOR SAID SHELF, SAID SHELF HAVING SUBSTANTIAL THICKNESS AND HAVING A CENTRAL LONGITUDINAL SLOT EXTENDING OVER SUBSTANTIALLY ITS ENTIRE LENGTH, A PAIR OF MUTUALLY OPPOSED TRACK ELEMENTS DISPOSED LONGITUDINALLY OF SAID SLOT AND WHOLLY INTERMEDIATE THE THICKNESS OF SAID SHELF, SAID COMPRESSOR HAVING PAIRS OF TRACK ELEMENT ENGAGING MEANS WHICH ARE SPACED APART AND ADAPTED TO LOOSELY ENGAGE SAID TRACK ELEMENTS, SAID TRACK ELEMENTS TERMINATING SHORT OF THE LENGTH OF SAID SLOT WHEREBY SAID COMPRESSOR MAY OCCUPLY ALTERNATIVELY A POSITION EXTENDING UPWARDLY FROM SAID SHELF OR DEPENDING DOWNWARDLY FROM SAID SHELF WITH SAID SPACED TRACK ENGAGING ELEMENTS IN OPERATIVE ENGAGEMENT WITH SAID TRACK ELEMENTS AND WITHOUT INTERFERING WITH BOOKS RESTING ON SAID SHELF OR EXTENDING UP TO SAID SHELF FROM BENEATH.