The tip part of the boss 7 is then heated and deformed by using a heating tool 20 having a shape covering the tip part of the boss 7 to block the outlet of the slit 8.
その後、ボス7の先端部にかぶさる形状の加熱具20でボス7の先端部を加熱し、変形させてスリット8の出口を塞ぐ。 - 特許庁
http://ejje.weblio.jp/sentence/content/+block+boss+