Something that lies on a face of the paper rather than through it. A chain of holes is not one: it goes through, and is on both faces at once.
Optional
The face of the roll it lies on: the side that faces the reader as the roll plays, or the back of it.
reo:side
Something that lies on a face of the paper rather than through it. A chain of holes is not one: it goes through, and is on both faces at once.