Completely Unnecessary. Just rip off the corner of the page. Simple, quick, done. I used to teach, dealt with that issue all the time, and never once used that evil Jaws-like contraption. Throw it out. You don't need it. (Also applies to letter-openers)
Sensitive issue here, I know. Many people would give up their life-sustaining morning cup of coffee rather than miss their "luxurious" soaks in the tub. Unless preceded by a shower, the reality of a bath is that you are lying in your own dirt/sweat/other bodily fluids we don't want to know about....Soothing? I don't believe in them, so I can't tell you, but probably yes. Sanitary? HellsNO! OPEN the drain. Keep it open. Always.