Hook: Floor Small (Green Square)The Security Mainframe decoration fits into a small green square floor hook.
Hook: Floor Medium Narrow (Blue Rectangle)The Security Mainframe decoration fits into a narrow blue medium rectangle floor hook.
Hook: Floor Medium (Blue Square)The Security Mainframe decoration fits into a blue medium square floor hook.
How to Get a Security Mainframe Decoration
Gathering Lockbox Decorations
Conquest Decorations rewards, sometimes known as crafting nodes, used to be extremely abundant with three being given every time you completed a conquest. In Update 7.0, Conquest stopped rewarding the Gathering Lockbox item with the random crafting node decorations, so the source of these have mostly dried up.
You can however get some every time you complete the one-time Stronghold introductory quest – some time after you complete it, you will receive a mail titled Planetary Conquest with the reward of Gathering Lockbox (Basic). The quest is one-time, but it’s very easy, and you can run it once on every one of your level 15+ characters, and the lockbox contains 4 random crafting node decorations.
You can also buy/sell them on the GTN.
These rewards are considered “useful” because you can right-click them to get some free crafting materials. Each decoration gives a slightly different set of materials. When you click one, you’ll then get a debuff preventing you from using another one for 30 minutes with a bit of randomization involved.