Baseball pitcher's practice device

Claim 1

A BASEBALL PRACTICE DEVICE FOR DEFINING A STRIKE ZONE FOR PITCHERS, COMPRISING, IN COMBINATION: A FRAME STRUCTURE INCLUDING TWO GENERALLY VERTICALLY EXTENDING PARALLEL UPRIGHT MEMBERS SPACED APART BY A DISTANCE GREATER THAN THE HORIZONTAL WIDTH OF SAID STRIKE ZONE; UPPER AND LOWER CROSS MEMBERS COUPLED TO THE UPPER AND LOWER ENDS OF SAID UPRIGHT MEMBERS RESPECTIVELY TO DEFINE A RECTANGULAR SHAPED FRAME; LEFT AND RIGHT VERTICALLY EXTENDING PARALLEL LINES CONNECTED BETWEEN SAID UPPER AND LOWER CROSS MEMBERS AND SPACED APART AT A HORIZONTAL DISTANCE CORRESPONDING TO THE HORIZONTAL WIDTH OF SAID STRIKE ZONE; AND UPPER AND LOWER HORIZONTALLY EXTENDING PARALLEL ELASTIC CORDS STRETCHED BETWEEN SAID UPRIGHT MEMBERS TO DEFINE WITH SAID LINES A SMALLER RECTANGLE CONSTITUTING SAID STRIKE ZONE, THE ENDS OF SAID ELASTIC CORDS BEING LOOPED ABOUT SAID UPRIGHT MEMBER IN FRICTIONAL ENGAGEMENT THEREWITH WHEREBY THEY MAY BE VERTICALLY MOVED ALONG SAID UPRIGHT MEMBERS TO VARY THE HEIGHT OF SAID ELASTIC CORDS AND THEREBY ENABLE ADJUSTMENT OF THE VERTICAL HEIGHT OF SAID STRIKE ZONE.