in fig1 hand - held plier stapler 10 includes handle unit 11 ( shown in section in fig1 ) which unit in turn consists of first handle 12 ; staple head unit 13 ; staple cartridge housing 14 and staple driving linkage cavity 16 . also shown are second handle 17 , staple blank belt cartridge 18 , pivotal anvil 19 , and removable cover 21 ( see also fig2 ). staple head unit 13 includes a block 23 made of light material , such as plastic ; metal face plate 24 and staple head 26 . face plate 24 is mounted on block 23 using locating nipples 28 on block 23 which receive circular opening 29 in plate 24 . head 26 is spaced from plate 24 by spacer lugs 30 which protrude from head 26 . such spacing provides a staple discharge channel defining the path through which staple blanks pass as they are formed and driven toward anvil 19 . stapling is accomplished by the delivery of staple blanks seriatim in belt form to groove 32 in staple block 33 . block 33 is mounted in opening 34 in head 26 and held against the head 26 by spring 36 engageable in head side holes 35 . the staple belt is delivered to staple block 33 by cartridge 18 fitted in a chamber ( not shown ) within block 23 . the cartridge chute 37 is located with its projections 38 extending through block opening 39 and plate opening 41 . projections 38 abut staple head 26 . the staple blanks are formed and driven in a single upward stroke by former 42 and driver 43 . the driver 43 drives the former 42 upwardly causing the prongs 44 of former 42 to engage and bend the staple blank to form a staple . as driver 43 continues in its upward movement , its flexible arms 42a are cammed to permit driver 43 to slide in frictional engagement relative to the former 42 . now with reference to all figures , the arrangement for driving upwardly and thereafter retracting the driver 43 with respect to the pivotal anvil 19 includes second handle 17 mounted about guide rod 46 which rod 46 is in turn mounted in the first handle bushings 47 . rod 46 is fixed relative to the first handle 12 and spans the cavity 16 . second handle 17 includes a body section 48 preferably made of plastic having upper and lower recesses 49 , 51 respectively . the upper recess 49 carries two spaced - apart lever plates 52 , 53 each having a slot 52a , 53a to receive guide rod 46 . spring 45 is mounted on guide rod 46 and spring rod 54 to urge pivot rod 57 upwardly which opens handles 12 , 17 ( see fig2 ). spring rod 54 is journaled in bushings 50 . lever plate holes 55 , 56 receive pivot pin 57 . anvil control arms 58 , 59 are also mounted on pivot pin 57 . lever plates 52 , 53 also include holes 52b , 53b to receive pivot pin 61 for connecting driver extension elongated link 62 . anvil 19 is pivotally mounted about anvil pivot axle 63 which axle also carries cartridge retainer spring 64 . anvil side arms 66 , 67 are pivotally connected to anvil puller arms 58 , 59 about axis 65 . driver pusher link 62 is pivotally connected to spaced apart legs 68 , 69 of driver connection piece 71 employing pivot rod 72 whose end portions ride in housing slots 73 . coil spribg 74 , with lower hook 76 engaging spring bar 77 and upper hook 78 engaging pivot rod 72 , urges the driver 43 and driver connection 71 downwardly into the retracted position ( fig2 ). extension hook 80 of connection 71 engages driver 43 through hole 79 . coil spring 74 functions to maintain a compressive pressure on the workpiece 82 during the stapling stroke and , upon completion of the stapling stroke , to return the mechanism to its retracted position . in the operation of the plier tool 10 , the workpiece 82 ( fig2 ) is placed between anvil 19 and the stapler head 26 with the handles 12 , 17 in their relaxed spaced - apart positions and with the anvil 19 in its upper position ( fig2 ). in this rest position , control rod 46 is in an intermediary position in slots 52a , 53a and rod 72 is at the bottom of housing slots 73 ( see fig2 ). to set the staple , second handle 17 is moved toward first handle 12 causing anvil arms 66 , 67 to move downwardly pulling anvil 19 down against the workpiece 82 ( see fig3 ). as the second handle 17 is moved further toward first handle 12 , the point of principal rotation of the second handle becomes pivot rod 57 . turning finally to fig4 continuing second handle 17 rotation causes the driver extension link 62 having centerline a to move closer to a position parallel to the path b of reciprocation of the former 42 and driver 43 . the angle c between lines a and b is an acute angle in the range of 20 ° to 30 °. driver extension link 62 engages pressure plate 75 as it moves during the power stroke . plate 75 is made of a hard material such as steel to reduce wear by rod 72 in slots 73 . plate 75 is mounted in a slot 70 in handle 12 ( see fig2 ). as pivot rod 72 moves upwardly in housing slots 73 an increased mechanical advantage ( or toggle effect ) is created . high forces are applied to driver 43 moving through small distances while lesser forces are required to be applied by the tool operator over greater distances . the tool is capable of stapling workpieces of varying thicknesses . the thickness of the workpiece dictates the extent of downward movement of the anvil arms 66 , 67 before the anvil &# 39 ; s engagement with ( and compression of ) workpiece 82 prevents the anvil arm &# 39 ; s further downward movement . slots 52a , 53a permit the second handle operation to adjust to the varying workpiece thicknesses . the variable thickness of workpiece 82 is compensated for by movement of spaced - apart plates 52 , 53 with slots 52a , 53a sliding up and down on guide rod 46 , thereby permitting handles 12 , 17 to engage at point d ( fig4 ) without any oversqueezing occurring .