Italian to English Other Construction / Civil Engineering Doors/Windows

This is all the context I have I'm afraid as it's from a door/window catalogue and just after a section on aluminium glazing beads. These appear to be unrelated terms ie 1) Distanziale aggancio 2) fermavetro alluminio and 3) cornice legno... so I think that it's the distanziale aggancio that I need help with. I've asked for a look at the catalogue but unfortunately there are no diagrams that could help. Thanks