A sheet material with a first fold line and a second fold line has been patented. The first and second fold lines are defined by a series of at least partial perforations in the sheet material. There are no partial perforations at an intersection of the first fold line and the second fold line. An intersection spacing is defined in a direction along either the first or second fold lines and is larger than the spacing between the partial perforations of the first or second fold lines. There is a non-perforated section at an intersection of a fold line with an edge of the sheet material. The at least partial perforations stop short of an intersection of a fold line with an edge of the sheet material.
Among at least one series of the partial perforations there is a further non-perforated section located between a first fold line intersection and one of a second fold line intersection and an intersection of a fold line with an edge of the sheet. In a direction along the at least one fold line the length of the further non-perforated section is greater than the spacing between the partial perforations.