embodiments of the present invention will now be described more fully with reference to the accompanying drawings . the invention may , however , be embodied in many different forms and should not be construed as being limited to the particular embodiments set forth herein ; rather , these embodiments are provided as through and complete disclosure and will fully convey the present invention to those skilled in the art . fig1 is a plan view illustrating a handler for testing semiconductor devices according to an embodiment of the present invention , and fig2 is a perspective view illustrating a method of determining the location of a test tray included in the handler of fig1 . more specifically , referring to fig1 , a test tray 100 is used for transferring semiconductor devices 11 . the test tray 100 according to an embodiment of the present invention can be used for loading ( mounting ) a plurality of semiconductor devices 11 , for directly testing the semiconductor devices 11 , and for unloading the semiconductor devices 11 after testing . in the subsequent descriptions , the use of a precise location - determining unit 130 for precisely determining a location of the test tray 100 under or in relation to the test head part is described , but it will be understood that the precise location - determining unit 130 can be used for a supply unit and a discharge unit , e . g ., in transport applications other than positioning relative to a test head part . the test tray 100 is first disposed in the supply unit . the plural semiconductor devices 11 are loaded on each of a plurality of transport modules 110 in the test tray 100 . the test tray 100 , on which the semiconductor devices 11 are loaded , is transferred to a test head part , e . g ., moving left - to - right in the view of fig1 and right - to - left in the view of fig2 . the test tray 100 is thereby transferred along a movement or transfer path by a driving force supplied from a motor 17 on a conveyor belt 19 in a movement direction indicated by an arrow in fig1 and 2 , and is initially stopped by a protrusion portion 12 of an end part of a stopper 13 selectively locatable in front of a leading portion 21 of the tray 100 . the protrusion portion 12 of the end part of the stopper 13 moves back and forth , e . g ., as a plunger movement , with respect to the stopper 13 . the location of the test tray 100 , as initially stopped by the stopper 13 , is further precisely determined and fixed by a precise location - determining unit 130 mounted on both sides of the test tray 100 and a positioner 15 . a locking hole 140 , depicted in fig2 , is included in the precise location - determining unit 130 of the test tray 100 , and the location of the test tray 100 is precisely determined and fixed by inserting a pin - shaped protrusion portion 14 of an end part of the positioner 15 into the locking hole 140 . the protrusion portion 14 of the positioner 15 is formed in a conical shape for easy insertion into the locking hole 140 . the protrusion portion 14 of the positioner 15 , or the entire positioner 15 , can selectively move back and forth . the test tray 100 can be continuously used , e . g ., without frequent maintenance or replacement , since a bushing 145 ( fig4 and 5 ) located in hole 140 prevents or substantially reduces wear of the locking hole 140 . if the bushing 145 is worn or damaged , the bushing 145 can be replaced without need to replace the entire test tray 100 . therefore , the test tray 100 can be used through extended periods without intervening maintenance or replacement procedures possibly affecting production rates . when a precise location of the test tray 100 is determined , a test for the semiconductor devices 11 loaded on the test tray 100 is performed . the test of the semiconductor devices 11 is performed by electrically contacting sockets or pin cards ( not shown ) located on a lower part of the test tray 100 , e . g ., by pressing the test tray 100 downward . a plurality of semiconductor devices 11 are tested simultaneously by mounting a plurality of electrically contacting portions between the sockets and the semiconductor devices 11 . with the protrusion portion 14 of the positioner 15 inserted into the locking hole 140 , the test can be stably performed in a fixed state of the test tray 100 . the test tray 100 , on which the tested semiconductor devices 11 remain loaded , is transferred to a discharge unit . the semiconductor devices 11 are then unloaded according to a classification of viable and failed devices . fig3 is a perspective view illustrating a test tray according to an embodiment of the present invention , and fig4 is an exploded perspective view of a precise location - determining unit of the test tray of fig3 . fig5 is an enlarged view of a precise location - determining unit of the test tray of fig3 , and fig6 is a cross - sectional view of the precise location determining unit of fig5 . referring to fig3 , a test tray 100 according to an embodiment of the present invention comprises a rectangular shaped frame 105 , horizontal bars 120 formed to cross both sides of the frame 105 to define a plurality of regions , a plurality of transport modules 110 along the horizontal bar 120 , and a tray recognition unit 125 mounted on a surface of the frame 105 . reference numeral 115 in the transport modules 110 indicates a semiconductor device - inserting unit on which semiconductor devices 11 ( not shown in fig3 ) are loaded . the precise location determining units 130 , that precisely determine the location and fix the test tray 100 , is mounted on both side portions 23 ( see fig2 ) of the test tray 100 . the precise location - determining units 130 , as depicted in fig2 , are located relative to , e . g ., along , a direction parallel to the moving direction of the test tray 100 within a handler system . the precise location - determining unit 130 is composed of a locking hole 140 in the frame 105 , a bushing 145 that is inserted in the locking hole 140 to prevent wearing of the locking hole 140 , a protection bar 135 that covers the frame 105 and the bushing 145 , and a connection hole 142 ( fig4 ) and a bolt 150 that couples the protection bar 135 and the frame 105 , e . g ., attaches the protection bar 135 to the frame 105 . the protection bar 135 is coupled to the frame 105 by being inserted into a concave area on each side of the frame 105 . the bushing 145 is formed , for example , of a polymer containing carbon fiber . thus , the compressive strength and stiffness of the bushing 145 can be increased and the expansion coefficient of the bushing 145 can be reduced . also , the bushing 145 can have high wearing resistance , high load carrying capability , and high thermal conductivity . also , as described above , the location of the test tray 100 is precisely determined and fixed since a positioner 15 ( see fig2 ) is inserted into the locking hole 140 of the precise location - determining unit 130 . in this manner , precise location - determining unit 130 and positioner 15 act as first and second locking formations each positionable relative to the other and mutually engagable to fix a selected position of the frame along the movement direction of the test tray 100 . furthermore , the test tray 100 can be continuously used since the bushing 145 prevents the locking hole 140 from wear . fig7 and 8 are perspective views respectively illustrating an undesirable wearing state of the locking hole 140 without a bushing 145 ( fig7 ) and an improved state of reduced or no wear when the bushing 145 is mounted in the locking hole 140 ( fig8 ). referring to fig7 and 8 , when the bushing 145 is mounted in the locking hole 140 of the precise location determining unit 130 of the test tray 100 according to embodiments of the present invention , as indicated by the reference numeral 160 in fig8 , the wearing of the locking hole 140 does not occur . however , as indicated by the reference numeral 155 in fig7 , when no bushing 145 is mounted in the locking hole 140 , the locking hole 140 is severely damaged , especially irregularly damaged . therefore , if the bushing 145 is inserted into the locking hole 140 of the precise location - determining unit 130 of the test tray 100 , the test tray 100 can be continuously used , e . g ., without intervening repair or replacement , since the wearing of the locking hole 140 is prevented . as described above , a test tray according to some embodiments of the present invention includes a precise location - determining unit that can precisely determine and fix the test tray on both side units of a frame in a direction parallel to the moving direction of the test tray in a handler . the precise location - determining unit includes a locking hole into which a positioner can be inserted , a bushing that can prevent the locking hole from wearing , a protection bar that covers the frame and the bushing , and a connection hole and a bolt to couple the protection bar to the frame . therefore , the test tray according to some embodiments of the present invention can solve conventional problems , such as a reduced yield , malfunction or sudden stopping of the handler , since a position of the test tray can be precisely determined when semiconductor devices are loaded , unloaded , and tested . furthermore , the test tray according to some embodiments of the present invention can be continuously used since the locking hole is prevented from wear by inserting a bushing into the locking hole when the locations of the test tray are precisely determined at a test head part , a supply unit , or a discharge unit . while the present invention has been particularly shown and described with reference to exemplary embodiments thereof , it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims .