the sheet 43 a the sheet immediately next to sheet 42 a with respect to the approach of incision s an embodiment is shown in fig4 b in this figure the incisions form a straight line 48 b along the left edge of the sheet 42 b in other words the line 48 b is between sheet 42 b and the sheet 43 b the sheet immediately next to sheet 42 b with respect to the approach of incision s another embodiment is shown in fig4 c in this figure the incisions form a zigzag line 48 c along the left edge of the sheet 42 c in other words the line 48 c is between sheet 42 c and the sheet 43 c the sheet immediately next to sheet 42 c with respect to the approach of incision s yet another embodiment is shown in fig4 d in this figure the incisions form a line or a course or progression 48 d characterized by round turns first to one side and then to the other the line 48 d is along the left edge of the sheet 42 d in other words the line 48 d is between sheet 42 d and the sheet 43 d the sheet immediately next to sheet 42 d with respect to the approach of weakened part s which is not shown in the drawings each sheet can be detachably attached to a sheet immediately next to it in the roll.