US Patent 7096641 Hollow profile

A hollow profile (1) formed of a flat material (31) having a width (d) has at least one groove (6.1, 6.2, 7.1, 7.2) provided on an outer side of at least one of the plurality of walls (2.1, 2.2, 5.1, 5.2) of the profile (1) and having a bottom (8.1, 8.2, 9.1, 9.2) spaced form the outer side by depth (t) and two opposite, substantially flat side walls (13.1, 13.2, 40.1, 40.2) extending substantially perpendicular to the bottom (8.1, 8.2, 9.1, 9.2), with the groove depth (t) of the at least one groove (6.1, 6.2, 7.1, 7.2, 32) amounting to from 0.5 to 2 times of the material thickness (d) of the flat material (31).