If it's laying around, Painter's tape (the blue stuff) is even better to use than any other tape, because there's no risk that it will pull up the varnish!
I just ran out of my manicure strips the other day and tried to freehand it (turned out terrible) It never occurred to me to just use tape, that's awesome! I'll have to try this out, especially because I find it very hard to justify $3 stickers just for my nails.
CO + K User
CO + K User
(:
I always draw the line with the white coat by hand, it's became always messy :s