Patent attributes
An hole-opening implement (5 or 50) for opening a hole in a soft material (2) has a first cutting part and a second cutting part. To pierce the soft material with the hole-opening implement, both cutting parts advances in the soft material while cutting the soft material. Such a state that the second cutting part remains in the soft material just after the first cutting part is passed through the soft material is assured so that a cut piece as bound to the soft material can remain after the opening. The first cutting part is formed at a tip of the hole-opening implement, and the second cutting part is disposed behind the first cutting part in the piercing direction of the hole-opening implement. Otherwise, the hole-opening implement may be constructed so that the first cutting part is sharp in section and the second cutting part is formed so as to have lower cutting force than the first cutting part.
