The term "perforated plate" (in practice often called perforated sheet) is defined in the latest edition of DIN 24041 as well as in DIN 4185 part 2. The term "perforated plate" according to the above DIN standards is a plate (sheet, panel etc.) with openings of a certain kind (holes) at regular intervals, made for example by punching, drilling, milling or other procedures. The simplest and most common shapes of holes are the round hole and the square hole; in addition, there are various types of long hole. More than 80 % of the perforated plates supplied have one of these main hole-shapes. Apart from that, there is a large number of special perforations for different kinds of application (mostly design).