Referring to FIGS 1, 2, 4 and 5 again, the wedge block 3 comprises a wedged base 31, two serrated portions 32 bilaterally disposed near the top, a center opening 33, and {TAIL ~ two dovetail projections} 34 bilaterally projecting into {HEAD ~ the center opening} 33 
Referring to FIGS 1 , 2 , 4 and 5 again , the wedge block 3 comprises a wedged base 31 , two serrated portions 32 bilaterally disposed near the top , a center opening 33 , and { TAIL ~ two dovetail projections } 34 bilaterally projecting into { HEAD ~ the center opening } 33
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