Guide to Stronghold Assault
Bloody Siege Warfare in the 41st Millenium

It's no secret that in 7th Edition, high Armour Value models are pretty good. However, not everyone plays Space Marines and has access to Land Raiders. So, how do you get in on the high armour Fortification action?

Fortification Upgrades
Fortication Upgrades
Small Buildings can have one, Medium Buildings can have two, Large Buildings can have three. Simple.
Ammo Store: Free Prescience. Nice.
Booby Traps: Doesn't work. If you show your opponent your list like you're supposed to, they'll never, ever fall for it. Although you could put an Objective on the Building and somehow force your opponent into it? ...Like Maelstrom Missions?
Escape Hatch: Instead of Disembarking from the Building's exit point, you can Disembark up to 12" away, that's really handy. Especially for last turn Objective grabs.
Magos Machine Spirit: The Building gains BS3.
Searchlights: Do the thing.
Void Shield: A Void Shield is an ablative Hull Point of AV12. It also gives your Building something similar to IWND. All for the price of a Power Fist. Do it.

Obstacles are up to 6" long and must be place wholly within 6" of the Fortification they were bought for. While you can purchase up to six of these things, remember that it's really hard to get larger pieces wholly within 6".
Tanglewire: A <6" long piece of Dangerous Terrain is kind of cool for 5 Points.
Barricades: Basically a <6" piece of Defense Line.
Tank Traps: Impassable Terrain to non-Skimmers and Dangerous Terrain to Bikes, and a Defense Line. Pretty solid.

Battlefield Debris
You can only have one of the below for each Fortification
Ammunition Dump: Similar to the Ammo Store, but also provides a cover save.
Comms Relay: Reserve manipulation. Some armies can make real use out of it. But most of the time you can ignore it.
Icarus Lascannon: Skyfire*, Interceptor Lascannon.
Quad-Gun: Two Twin-Linked Skyfire*, Interceptor Autocannons.
*Remember that this type of Skyfire can not be 'turned off'.

Aegis Defence Line: Funnily enough, it's a Defence Line. Due to it's weird Deployment style, you can do a lot of things with it. You can shore up a bottleneck (especially with extra Barricades), you can make a 'box' so that whatever is inside has a Cover Save from every angle. You'll figure it out. Look at your terrain, and place the Defence Line best. Basically, having a Defence Line is like gaining an extra Ruin, except better, because you get the equivalent of Stealth if you decided to Go To Ground behind it. Defence Lines are the cheapest way to grab Gun Emplacements for those people who still refuse to use Allies and have no other Flier Defense at all. If your army can shoot Fliers anyway, having a unit behind an Aegis Line with an Ammo Dump can make firefights pretty brutal.

Bastion: It's a Medium Building with AV14, with four Heavy Bolters that all have different Line of Sights. It's a solid model. If you can put a unit that has decent range in it (i.e; Missile Launchers), it's very tough. If you're worried about Deep Strikers - and this goes for all Buildings - just put up to six pieces of Tanglewire around it. If your opponent can't deploy their models, then they mishap. If they're using Drop Pods, the Tanglewire will take the 'Pod far enough away that Melta weapons will be out of Melta-range and need 6s to Glance your AV14.

Imperial Strongpoint: 1-5 Aegis Lines, 1-3 Bastions, 0-1 Skyshields, 0-1 Honoured Imperium. Ignore the 0-1 stuff. Ignore the 'Imperium' in the title. For the cost of one Aegis Line, you can take up to three more Bastions. This is excellent for non-Space Marines who want get in on the 'Land Raider meta' but don't have Land Raiders in their Codex. Yes, you still have to pay points for all this stuff, but, the point is that you can have several models in the same Fortification slot.

Honoured Imperium: Pay 40 Points to make Imperial units Stubborn. However, it's only 40 Points and you can take up to six Barricades anyway. But you should ignore this all the time...

Wall of Martyrs Imperial Defence Line: It's a Defence Line that gives Stubborn. Unfortunately, it can only be upgraded with Obstacles. No Skyfire or Ammo Dumps.

WoM Imperial Defence Emplacement: I don't know why this is less points than the above. Heavy weapons fired from this Wall can re-roll To-Hit when firing Overwatch.

WoM Imperial Bunker: WTF!? It's better than a Bastion for cheaper.

WoM Firestorm Redoubt: At least this one didn't tack on a misleading 'Imperial' title. Ignore all of those. Fortifications are for everyone. It's a Medium AV14 Building with two Gun Emplacements that have Automated Fire...BS2...Ergh. Luckily Quad Icarus Lascannons have two Twin-Linked shots. But, wouldn't you rather upgrade those Icarus Lascannons to Battle Cannons (yes, those) where the BS2 doesn't actually matter? Of course you would. Find your Skyfire somewhere else. Not here.

WoM Vengeance Weapon Battery: An immobile, BS2 Punisher Cannon with AV14 for 75 Points. BS2 is fine because a Punisher has 20 shots. What? Orks hit all the time. You can upgrade to a Battle Cannon, or a Quad Icarus Lascannon. If you don't have the manpower to actually fire a gun behind an Aegis Line - because all of your models are in Vehicles - then Vengeance weapons are right for you.

WoM Imperial Defence Network: Again, there's nothing special here. The real key to this type of Fortification is that you have multiple things in the same slot. Although you can always multi-CAD and pick an extra slot or two anyway. It's up to you.

Promethium Relay Pipe: Model them based off of the size of an Aegis Line, because that's what they are. Non-Vehicles firing Flamer weapons - as defined in the rulebook - may gain Heavy, Torrent. Just don't botch your Cover Saves, although, if you've got 4+ or better armour, it doesn't matter. Eldar Wraithguard gain no benefit because the list of which weapons this Fortification works with is specifically those found in the rulebook.

Void Shield Generator: It's projects a 'bubble' of AV12. So your opponent has to shoot with their anti-tank weapons first, and even then, it hits the VSG. In low point games - the VSG caps out at 100 Points, which is easily included - it's a terror. In high point games, players are going to pretend that it's an AV13 Super-Heavy with 3 Hull Points, and shut it down easily. Yes, at first it seems powerful, until you understand how it works. If your army can deal with multiple Knight Titans, then it should be able to deal with a VSG. However, Knight Titans inside a VSG is a different matter altogether.
Yes, there's an Official Model, but that's gone now. But, point is, there is an Official Model, so, you do have to use it as guideline if you want to make your own. Here's how big it is.

Void Relay Network: Any sane meta has already banned it. For the price of one Promethium Relay Pipe - 40 Points - you can have up to three Void Shield Generators. Yep. It's a thing. Although anyone willing to put in the conversion work for three VSGs deserves to have it. Three VSGs (340 Points ) and three - or more - Knight Titans. Thanks for playing.

Skyshield Landing Pad: Models on the top gain a 4++. That's solid, especially for Vehicles. So, you can deploy Vehicles on the top, if they want to move off, you roll forwards and take a difficult terrain check...Vehicles flying through the air. It can happen. If you choose not to take the 4++, you can have units that Deep Strike onto the top on the Skyshield not Scatter, which is useful, especially for large footprint Deep Strikers like Blood Angel Land Raiders - and then said Land Raider can drive off. For 5 Points, the Skyshield allows you to start with a Flier in Hover mode on the board, the only stipulation is that your Flier can't Zoom in the first turn. Before you start talking about how broken this is, check if the Flier you want to use can Hover, then think about what happens when your opponent sees a Flier in Hover in mode...

Fortress of Redemption: The Fortress of Redemption is is four Buildings with AV14, with a Missile Silo and Twin-Linked Icarus Lascannon. Before you go out and buy an Aegis Line three Bastions for your Strongpoint (275 Points, minimum), consider the Fortress of four Buildings instead (220 Points, with guns attached). So...Yeah. The Fortress is a good buy for any army, it's still cheaper even than a single Land Raider.

Macro-Cannon Aquila Strongpoint: It's 500+ Points. But, it's an AV15 Mighty Bulwark. If your meta likes to field Super-Heavies, but you don't have one of your own, Aquila Strongpoints come fairly easily from Games Workshop, and come with a two-shot Str-D weapon, and an Apocalyptic Mega-Blast weapon for killing Infantry. Basically, it's a Lord of War for people who don't have Lords of War. But, do you want to know what's terrifying? The Macro-Cannon is a Fortifcation. So if you want a Lord of War as well, you can!

Vortex Missile Aquila Strongpoint: 500+ Points. AV15 Mighty Bulwark. Unlimited range, Large Blast Vortecies. **** Void Shield Generators. This is where it's at - Void Hole Generators. It's exactly as good as it looks. If your opponent goes first, expect them to target this thing immediately, because then you get hit with a Vortex Missile, and that's the downside to this thing. So...You're probably better off with the Macro-Cannon, since when that explodes, it wont kill off another section of your own army.