The small sized thread crest provided at {TAIL ~ 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 the gypsum board and the C type steel plate structural material 
The small sized thread crest provided at { TAIL ~ 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 the gypsum board and the C type steel plate structural material
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