A high strength, flexible, foldable and printable sheet, such as a label sheet or cardstock, is provided with a line of weakness. The sheet has maximum dimensions greater than that of a box into which the sheet is to be located, and is therefore folded flat to fit into the box. The sheet is later removed, and may be printed in a laser or ink jet printer or copier. The sheet is formed to have a tensile strength of at least 4.5 or 5.0 or more kilograms, across the line of weakness, so that it will reliably feed through an office type printer or copier.