Dual square

Claim 1

A SQUARE COMPRISING IN COMBINATION, A HEAD HAVING A GRADUATED RULE, FORMED WITH A GROOVE ALONG ONE FACE THEREOF, THAT IS RELEASABLY SECURED TO THE HEAD SLOTTED TO RECEIVE THE SAID RULE, SAID HEAD BEING FORMED WITH A BORE IN THE PLANE OF SAID SLOT AND WITH A CLAMPING STUD RECEIVED IN SAID BORE, ITS END WITHIN THE CONFINES OF SAID SLOT BEING FORMED TO PRESENT A FINGER HAVING AT ITS FREE END A TRANSVERSE RIB TO BE RECEIVED IN SAID GROOVE IN SAID FACE OF THE SAID RULE, AND SAID TRANSVERSE RIB ON SAID FINGER OF SAID STUD MAY BE PRESENTED TO SAID GROOVE IN SAID RULE TO ENGAGE EITHER FACE OF SAID RULE TO EITHER SIDE OF SAID HEAD, SAID HEAD TO EXTEND LATERALLY THEREFROM SAID RULE AND HAVING A SIDE EDGE DISPOSED TO EXTEND AT A RIGHT ANGLE TO SAID RULE AND ALSO HAVING ANOTHER EDGE EXTENDING AT AN OBLIQUE ANGLE TO THE FIRST MENTIONED EDGE, SAID HEAD HAVING AN APERTURE ADJACENT TO THE FIRST SAID EDGE AND SAID APERTURE BEING REMOTE FROM SAID RULE AND LEADING INTO AN INCLOSED CAVITY WITHIN SAID HEAD WHEREIN A RESILIENT GRADUATED, FLEXIBLE MEASURING TAPE OF CONCAVO-CONVEX CROSSSECTIONAL SHAPE AND A SPIRALLY COILED SPRING MEANS ANCHORED AT ITS INNER END TO SAID HEAD IS HOUSED SAID SPRINGS OUTER END BEING OPERATIVELY SECURED TO SAID TAPE, AND TENDING TO HOLD SAID TAPE IN ITS WOUND POSITION, THE ARRANGEMENT BEING SUCH THAT SAID TAPE WHEN BEING PULLED FROM SAID HEAD SERVES TO WIND SAID SPRING UPON ITSELF, THE RESILIENCE OF SAID TAPE AND THE RESILIENCE OF SAID SPRING BEING SO CORRELATED THAT THE STRENGTH OF SAID SPRING IS SUFFICIENT TO FACILITATE THE COILING OF SAID TAPE WHEN THE EXTENDED PORTION OF SAID TAPE IS FED INTO SAID CAVITY, AND ANY UNDERSIRABLE DEGREE OF FRICTIONAL ENGAGEMENT BETWEEN THE CONVOLUTIONS OF THE TAPE AND THE WALL OF THE CAVITY IS SUBSTANTIALLY AVOIDED, AND WHEN SAID TAPE IS DRAWN OUT THROUGH SAID APERTURE IT THEREBY FORMS AN EXTENSION OF THE FIRST SAID EDGE, AND A TAPE LOCK LOCATED IN SAID CAVITY ADJACENT TO SAID TAPE FOR RELEASABLY LOCKING SAID CONCAVO-CONVEX TAPE IN AN EXTENDED POSITION AND SAID TAPE HAS ON ITS EXTENDED END A HOOK SECURED THERETO.