the present invention refers to a system for packing , storing and transporting , particularly in a vertical position , stacks of sheet material such as glass , metal , plastic and large marble plates . the invention provides , for use in packing , storing and transporting sheet material , a sheet material protecting unit including two complementary protecting elements , each including a substantially planar surface for engaging a surface of the sheet material and at least one coupling element for coupling the two protecting elements about the sheet material , wherein the sheet material protecting unit is characterized in that the coupling element is of adjustable length which can be shortened on site during packing according to the thickness of the packed sheet material .