HVAC- it looks like a toy security gate or grave stones (Another use?)
Bicycle inner tube tar over asphalt. Or in my case, semi truck tube used for floating down rivers years ago 
.The thickness varies and corresponds to use mostly.(I bought the thick ones considering branch pokes 
)
When you don't buy your socks in a five gallon bag 
(hordious bromhidrosis ) they often come on a funny little hanger for the closet. Trim the hanger portion off paint as seen fit, and you have a section of fence. (2 upside down to see the trim spot here)
The same hanger curved in boiling water is a radar antenna...
(Micro wave transmitter, radio,etc)
They also have been used as loading ramps, platform grates, scaffold flats, and bridge catwalk. (Right of Gantry, top of spot light pole, it's also sitting free, on a wire terminal s finger nut like a cover)
That pole and huge spot lights are one of those cross bucks we aquire as "ka-nick ka-knak gifts”( ) we all aquire as gifts repeatedly, then break the extras while rummaging in storage. (I think this was #4 downstairs, lol)
The whole thing sits over a passtrough base of wood and hardboard from old stereo equipment I was tossing. Its 'tunnel' will have hardwood doors that slide on c-channel and bi-fold door wheels. All stuff accumulated for household repairs ahead of time.
Wow, There's lots in this shot.
The rocket low on the right of the gantry a thick (vintage) gift paper tube, the nosecone a plastic end cap for a hollow broomstick, sanded/filed.
To the left is a Stanley tool package raised roof on a styrene body crane and platform, and a boom of a tone arm from a Sansui linear tracking turntable (Ooops....record player is a better word here, eh? )
The yard spot on the lionel arch is a kitchen spice rack/shelf dowel and a cake decorating top hat with a bulb socket in it. Crude but try looking close when lit lol.
The extension beam supporting the track, is old adjustable shelf support C-bracket 2/cut short, with a nut and bolt to form a long clamp grabbing the arches top at the original track-nut plate's slots. There is a small catwalk on it of scrap styrene here, hard to see the beam.
Top right, an upside down lazer pointer cap, inverted like a vase, is a vintage desk flags light sconce.
)......
