how can i find wire mesh in online bcl?

edit

thank @David Goldwasser i already download the attic construction set from the construction assemblies and use it, but when i made my layer materials for roof construction didn't find the wire mesh and roof trusses. can i ignore these two layers while i use the attic construction set?? if not, how can i define my truss???

and for attic floor i download the construction set and assign it as interior ceiling, is it right?

Yes, to either assign it to the ceiling of the space below the attic, or the floor of the attic.