Subclass 1/20: Border constructions of openings in walls, floors, or ceilings; Frames to be rigidly mounted in such openings (E06B 5/00 takes precedence; features relating also to inner frames or wing frames, features relating solely to the mounting of inner frames E06B 3/00; corner joints or edge joints E06B 3/96) Frames for doors, windows, or the like to be fixed in openings (special adaptations for fixing in base frames E06B 1/02; features relating solely to the mounting of glass panes or other sheets E06B 3/00) Metal frames composed of several parts with respect to the cross-section of the frame itself adjustable with respect to the thickness of walls