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Claim 1

A THUMB CUFF COMPRISING A PAIR OF CLOSELY SPACED PARALLEL SIDE PLATES PROVIDED WITH OPPOSITELY DIRECTED CURVED CRADLE ARMS AT THE OPPOSITE ENDS THEREOF, UPPER AND LOWER VERTICALLY DISPLACED SPACER BLOCKS DISPOSED BETWEEN SAID SIDE PLATES AND SERVING TO MAINTAIN THE LATTER IN THEIR CLOSELY SPACED RELATIONSHIP, SAID SPACER BLOCKS AND SIDE PLATES DEFINING AN INTERNAL OPERATING CHAMBER, CURVED CLAMPING ARMS PIVOTALLY CONNECTED TO THE DISTAL ENDS OF SAID CRADLE ARMS AND CAPABLE OF REENTRANT SWINGING MOVEMENT IN OPPOSITE DIRECTIONS RESPECTIVELY BETWEEN THE CRADLE ARMS TO DEFINE IN COMBINATION THEREWITH TWO VARIABLE-SIZE THUMB-ENGAGING OPENINGS, A PAIR OF LATCHING PAWLS PIVOTALLY MOUNTED WITHIN SAID OPERATING CHAMBER, RATCHET TEETH ON SAID CLAMPING ARMS AND MOVABLE INTO LOCKING RELATION WITH RESPECT TO SAID PAWLS DURING REETRANT SWINGING MOVEMENT OF THE CLAMPING ARMS, A SPRING DISPOSED WITHIN SAID CHAMBER, HAVING A BIGHT PORTION SEATED WITHIN A RECESS PROVIDED IN THE UPPER SPACER BLOCK AND HAVING SUBSTANTIALLY PARALLEL SPRING ARMS BEARING AGAINST SAID PAWLS FOR URGING THE SAME OUTWARDLY INTO OPERATIVE ENGAGEMENT WITH THE RATCHET TEETH ON THE CLAMPING ARMS, THE UPPER SPACER BLOCK HAVING PORTIONS DISPOSED IN THE PATHS OF MOVEMENT OF THE PAWLS TO LIMIT THE OUTWARD MOVEMENT OF THE LATTER, THE LOWER SPACER BLOCK HAVING PORTIONS DISPOSED IN THE PATHS OF MOVEMENT OF THE PAWLS TO LIMIT THE INWARD MOVEMENT OF THE LATTER, AND PROJECTIONS ON SAID PAWL SELECTIVELY ENGAGEABLE WITH A KEY FOR MOVING THE PAWLS OUT OF LOCKING RELATION WITH SAID RATCHET TEETH.