The small sized thread crest provided at the smaller parallel thread part 15 generates driving force in the inserting direction of the screw upon its rotation so that the parallel thread part 13 is screwed into the steel plate, resulting in {HEAD ~ fixation} of {TAIL ~ the gypsum board} and the C type steel plate structural material 
The small sized thread crest provided at the smaller parallel thread part 15 generates driving force in the inserting direction of the screw upon its rotation so that the parallel thread part 13 is screwed into the steel plate , resulting in { HEAD ~ fixation } of { TAIL ~ the gypsum board } and the C type steel plate structural material
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