It's called cable rail which you can buy from the company of the same name or just buy parts from Mcmaster-carr. This rail needed steel supports to make the profile thinner but we lined the double posts with wood to integrate better with the house. Thanks for your comments!

Thanks for such a quick response it is going on my list for the deck.
Michelle

Sorry for the delay. It's just pressure treated pine. The photo was taken prior to staining but after it had weathered enough to receive a finish. Hope this helps.

Your design is beautiful. I am thinking of putting a fireplace on our deck. But, I heard that you should not put a fireplace on a wood deck or pressure treated wood. Isn't that dangerous. Have you ever used Aluminum decks in stead of pressure treated and have you used this type of decking before, This material is fire resistant.

Thanks for your comment. Yes, you need to have a non-combustible surface directly in front of the fire place as well as the surfaces surrounding the opening (each manufacturer will have different requirements in terms of the amount/extent of non-combustible material depending on UL label, type and location, including noting how far away a mantel can be from the opening). Metal decks solve the problem in terms of the floor. However, you do not specifically have to use a metal or completely non-combustible deck in order to do this. The trick is to create a layer of fire protection between the deck and the fireplace. One way to solve this if the deck already exists is to cut out the deck boards directly in front of where the fireplace will be and put down a sheet of hardi-plank or other fiber-cement board and secure it to the joists, covering it with a layer of non-combustible tile mortared to the fiber panel. You have to make sure the structure can support the added load and the deck joists and remaining deck boards are secured with additional joists or other structural components. Another option is to purchase a prefabricated hearth extender, but not all are rated for exterior use. Check with the manufacturer as well as an engineer, architect, or qualified experienced contractor in your area for how you would address your specific condition. Finally, if you like the look and feel of metal decks and can afford their relatively high price, they are a great option in terms of long term low maintenance. Hope this helps.