alternative embodiment includes grooves of varying depth in which case the groove areas would not all lie in a single plane parallel to a surface plane that is in the alternative embodiment the groove areas do not lie in a plane or lie in a plane that is not parallel to either the top surface plane or bottom surface plane furthermore it is possible to vary the height of the land areas such that the top surface of the layer has an uneven construction and the land areas no longer lie in a single plane still further it is noted that in the fig2 embodiment some perforations lie partly in a groove and partly in a land it is possible to form the layer such that each perforation lies either entirely in a groove or entirely in a land with no perforation lying across a land groove interface in any event the perforations may be formed either before or after grooves are formed it is also conceivable that the grooves can be at an angle with the machine direction furthermore there can be two series of grooves at an angle to each other in a cross hatch pattern fig3 is a plan view of a section of a perforated layer in accordance with another embodiment of the invention as can be seen from fig3 all perforations.