Index: binaries/data/mods/public/globalscripts/Templates.js
===================================================================
--- binaries/data/mods/public/globalscripts/Templates.js
+++ binaries/data/mods/public/globalscripts/Templates.js
@@ -273,6 +273,9 @@
 			if (template.BuildRestrictions.Distance.MaxDistance)
 				ret.buildRestrictions.distance.max = getEntityValue("BuildRestrictions/Distance/MaxDistance");
 		}
+
+		if (template.BuildRestrictions.Sockets)
+			ret.buildRestrictions.sockets = template.BuildRestrictions.Sockets._string.split(/\s+/);
 	}
 
 	if (template.TrainingRestrictions)
Index: binaries/data/mods/public/gui/session/input.js
===================================================================
--- binaries/data/mods/public/gui/session/input.js
+++ binaries/data/mods/public/gui/session/input.js
@@ -131,11 +131,14 @@
 	{
 		if (placementSupport.template && placementSupport.position)
 		{
-			var result = Engine.GuiInterfaceCall("SetBuildingPlacementPreview", {
+			let result = Engine.GuiInterfaceCall("SetBuildingPlacementPreview", {
 				"template": placementSupport.template,
 				"x": placementSupport.position.x,
 				"z": placementSupport.position.z,
 				"angle": placementSupport.angle,
+				"snapClasses": placementSupport.socketSnapClasses,
+				// Ideally we'd only get entities with certain class.
+				"snapEntities": placementSupport.socketSnapClasses.length && Engine.GetEntitiesWithStaticObstructionOnScreen(),
 				"actorSeed": placementSupport.actorSeed
 			});
 
@@ -176,7 +179,7 @@
 				placementSupport.tooltipMessage = sprintf(translatePlural("Basic range: %(range)s meter", "Basic range: %(range)s meters", range), { "range": range }) + "\n" +
 					sprintf(translatePlural("Average bonus range: %(range)s meter", "Average bonus range: %(range)s meters", averageRange), { "range": averageRange });
 			}
-			return true;
+			return result;
 		}
 	}
 	else if (placementSupport.mode === "wall")
@@ -296,7 +299,8 @@
 		return false;
 	}
 
-	if (!updateBuildingPlacementPreview())
+	let buildingPlacementInfo = updateBuildingPlacementPreview();
+	if (!buildingPlacementInfo)
 	{
 		// invalid location - don't build it
 		// TODO: play a sound?
@@ -308,14 +312,15 @@
 	Engine.PostNetworkCommand({
 		"type": "construct",
 		"template": placementSupport.template,
-		"x": placementSupport.position.x,
-		"z": placementSupport.position.z,
+		"x": buildingPlacementInfo.x,
+		"z": buildingPlacementInfo.z,
 		"angle": placementSupport.angle,
 		"actorSeed": placementSupport.actorSeed,
 		"entities": selection,
 		"autorepair": true,
 		"autocontinue": true,
-		"queued": queued
+		"queued": queued,
+		"snapEntity": buildingPlacementInfo.snappedEnt
 	});
 	Engine.GuiInterfaceCall("PlaySound", { "name": "order_build", "entity": selection[0] });
 
@@ -1086,21 +1091,19 @@
 				{
 					placementSupport.position = Engine.GetTerrainAtScreenPoint(ev.x, ev.y);
 
-					if (isSnapToEdgesEnabled())
+					let snapData = Engine.GuiInterfaceCall("GetFoundationSnapData", {
+						"template": placementSupport.template,
+						"x": placementSupport.position.x,
+						"z": placementSupport.position.z,
+						"snapEntities": placementSupport.socketSnapEntities,
+						"snapToEdges": isSnapToEdgesEnabled() && Engine.GetEdgesOfStaticObstructionsOnScreenNearTo(
+							placementSupport.position.x, placementSupport.position.z)
+					});
+					if (snapData)
 					{
-						let snapData = Engine.GuiInterfaceCall("GetFoundationSnapData", {
-							"template": placementSupport.template,
-							"x": placementSupport.position.x,
-							"z": placementSupport.position.z,
-							"snapToEdges": Engine.GetEdgesOfStaticObstructionsOnScreenNearTo(
-								placementSupport.position.x, placementSupport.position.z)
-						});
-						if (snapData)
-						{
-							placementSupport.angle = snapData.angle;
-							placementSupport.position.x = snapData.x;
-							placementSupport.position.z = snapData.z;
-						}
+						placementSupport.angle = snapData.angle;
+						placementSupport.position.x = snapData.x;
+						placementSupport.position.z = snapData.z;
 					}
 
 					g_DragStart = new Vector2D(ev.x, ev.y);
@@ -1311,6 +1314,7 @@
 		placementSupport.mode = "building";
 		placementSupport.template = buildTemplate;
 		inputState = INPUT_BUILDING_PLACEMENT;
+		placementSupport.socketSnapClasses = templateData.buildRestrictions.sockets || [];
 	}
 
 	if (templateData.attack &&
Index: binaries/data/mods/public/gui/session/placement.js
===================================================================
--- binaries/data/mods/public/gui/session/placement.js
+++ binaries/data/mods/public/gui/session/placement.js
@@ -15,6 +15,8 @@
 	this.template = null;
 	this.tooltipMessage = "";        // tooltip text to show while the user is placing a structure
 	this.tooltipError = false;
+	this.socketClasses = null;
+	this.socketSnapEntities = null;
 	this.wallSet = null;             // maps types of wall pieces ("tower", "long", "short", ...) to template names
 	this.wallSnapEntities = null;    // list of candidate entities to snap the starting and (!) ending positions to when building walls
 	this.wallEndPosition = null;
Index: binaries/data/mods/public/simulation/components/BuildRestrictions.js
===================================================================
--- binaries/data/mods/public/simulation/components/BuildRestrictions.js
+++ binaries/data/mods/public/simulation/components/BuildRestrictions.js
@@ -18,6 +18,7 @@
 			"<value>land</value>" +
 			"<value>shore</value>" +
 			"<value>land-shore</value>"+
+			"<value>socket</value>"+
 		"</choice>" +
 	"</element>" +
 	"<element name='Territory' a:help='Specifies territory type restrictions for this building.'>" +
@@ -45,11 +46,23 @@
 				"<optional><element name='MaxDistance'><data type='positiveInteger'/></element></optional>" +
 			"</interleave>" +
 		"</element>" +
+	"</optional>" +
+	"<optional>" +
+		"<element name='Sockets' a:help='Specifies the socket classes this building must be placed upon.'>" +
+			"<attribute name='datatype'>" +
+				"<value>tokens</value>" +
+			"</attribute>" +
+			"<text/>" +
+		"</element>" +
 	"</optional>";
 
 BuildRestrictions.prototype.Init = function()
 {
 	this.territories = this.template.Territory.split(/\s+/);
+	if (this.template.Sockets)
+		this.sockets = this.template.Sockets._string.split(/\s+/);
+	if (this.template.PlacementType == "socket" && !this.sockets)
+		warn("Placement type 'Socket' without a socket specified, this building (" + this.entity + ") can never be built.");
 };
 
 /**
@@ -144,7 +157,8 @@
 		var ret = cmpObstruction.CheckFoundation(passClassName, false);
 	}
 
-	if (ret != "success")
+	// When a socket is needed obstruction ought to be ignored.
+	if (ret != "success" && this.template.PlacementType != "socket")
 	{
 		switch (ret)
 		{
@@ -230,6 +244,12 @@
 		}
 	}
 
+	if (this.template.PlacementType == "socket" && !this.CheckSocketPlacement(pos))
+	{
+		result.message = markForTranslation("%(name)s must be built on a valid socket.");
+		return result;	// Fail
+	}
+
 	let cmpTemplateManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_TemplateManager);
 
 	let templateName = cmpTemplateManager.GetCurrentTemplateName(this.entity);
@@ -298,6 +318,24 @@
 	return result;
 };
 
+/**
+ * Whether this entity is placed on the correct socket.
+ */
+BuildRestrictions.prototype.CheckSocketPlacement = function()
+{
+	let cmpRangeManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_RangeManager);
+	let classes = this.sockets;
+
+	let filter = function(id)
+	{
+		let cmpIdentity = Engine.QueryInterface(id, IID_Identity);
+		return cmpIdentity && MatchesClassList(classes, cmpIdentity.GetClassesList());
+	};
+	let cmpPlayerManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_PlayerManager);
+
+	return cmpRangeManager.ExecuteQuery(this.entity, 0, 0, cmpPlayerManager.GetAllPlayers(), IID_BuildSlot).some(filter);
+};
+
 BuildRestrictions.prototype.GetCategory = function()
 {
 	return this.template.Category;
Index: binaries/data/mods/public/simulation/components/BuildSlot.js
===================================================================
--- binaries/data/mods/public/simulation/components/BuildSlot.js
+++ binaries/data/mods/public/simulation/components/BuildSlot.js
@@ -1,10 +1,3 @@
-function Settlement() {}
-
-Settlement.prototype.Schema =
-	"<empty/>";
-
-Engine.RegisterComponentType(IID_Settlement, "Settlement", Settlement);
-
 /*
  * TODO: the vague plan is that this should keep track of who currently owns the settlement,
  * and some other code can detect this (or get notified of changes) when it needs to.
@@ -13,3 +6,98 @@
  * tell us that its player owns us, and move us back into our original position when the building
  * is destroyed. Don't know if that's a sensible plan, though.
  */
+class BuildSlot
+{
+	Init()
+	{
+		this.occupant = INVALID_ENTITY;
+	}
+
+	/**
+	 * Initialises construction, thus rendering this socket useless.
+	 *
+	 * @param {number} player - The player requesting the initialisation.
+	 * @param {number} entity - The entity being built on/in this slot.
+	 *
+	 * @return {boolean} Whether the initialisation was successful.
+	 */
+	InitConstruction(entity)
+	{
+		this.occupant = entity;
+
+		if (this.template.HideUponUse != "true")
+			return true;
+
+		let cmpPosition = Engine.QueryInterface(this.entity, IID_Position);
+		if (!cmpPosition)
+			return false;
+
+		this.previousPosition = cmpPosition.GetPosition();
+		cmpPosition.MoveOutOfWorld();
+
+		return true;
+	}
+
+	/**
+	 * Resets this socket by setting the owner to -1 and moving back to its former position.
+	 */
+	Reset()
+	{
+		this.occupant = INVALID_ENTITY;
+
+		if (!this.previousPosition)
+			return;
+
+		let cmpPosition = Engine.QueryInterface(this.entity, IID_Position);
+		if (!cmpPosition)
+			return;
+
+		cmpPosition.JumpTo(this.previousPosition.x, this.previousPosition.z);
+		delete this.previousPosition;
+	}
+
+	/**
+	 * Get the current owner.
+	 *
+	 * @return {number} The current owner of this build slot.
+	 */
+	GetOccupant()
+	{
+		return this.occupant;
+	}
+}
+
+BuildSlot.prototype.Schema =
+	"<a:help>Specifies this is a building slot, an entity where a structure can be placed upon.</a:help>" +
+	"<a:example>" +
+		"<BuildSlot>" +
+			"<HideUponUse>true</HideUponUse>" +
+		"</BuildSlot>" +
+	"</a:example>" +
+	"<element name='HideUponUse' a:help='Whether the slot will be hidden when construction initiates.'>" +
+		"<data type='boolean'/>" +
+	"</element>";
+
+BuildSlot.prototype.OnGlobalEntityRenamed = function(msg)
+{
+	if (msg.entity != this.occupant)
+		return;
+
+	// Our occupant died, reset our state.
+	if (msg.newentity == INVALID_ENTITY)
+		this.Reset();
+	else
+		this.occupant = msg.newentity;
+};
+
+BuildSlot.prototype.OnGlobalOwnershipChanged = function(msg)
+{
+	if (msg.entity != this.occupant)
+		return;
+
+	// Our occupant died, reset our state.
+	if (msg.to == INVALID_PLAYER)
+		this.Reset();
+};
+
+Engine.RegisterComponentType(IID_BuildSlot, "BuildSlot", BuildSlot);
Index: binaries/data/mods/public/simulation/components/GuiInterface.js
===================================================================
--- binaries/data/mods/public/simulation/components/GuiInterface.js
+++ binaries/data/mods/public/simulation/components/GuiInterface.js
@@ -1041,6 +1041,30 @@
 		"translateParameters": [],
 	};
 
+	let snapData;
+	if (cmd.snapEntities)
+	{
+		let snapRadius = 10; // ToDo: Adapt.
+		snapData = this.GetFoundationSnapData(player, {
+			"x": cmd.x,
+			"z": cmd.z,
+			"template": cmd.template,
+			"snapEntities": cmd.snapEntities,
+			"snapRadius": snapRadius,
+		});
+
+		if (snapData)
+		{
+			cmd.x = snapData.x;
+			cmd.z = snapData.z;
+			cmd.angle = snapData.angle;
+			cmd.snapped = true;
+
+			if (snapData.ent)
+				cmd.snappedEnt = snapData.ent;
+		}
+	}
+
 	// See if we're changing template
 	if (!this.placementEntity || this.placementEntity[0] != cmd.template)
 	{
@@ -1077,6 +1101,16 @@
 		else
 			result = cmpBuildRestrictions.CheckPlacement();
 
+		result.x = cmd.x;
+		result.z = cmd.z;
+		if (snapData)
+		{
+			result.x = snapData.x;
+			result.z = snapData.z;
+			if (snapData.ent)
+				result.snappedEnt = snapData.ent
+		}
+
 		let cmpRangeOverlayManager = Engine.QueryInterface(ent, IID_RangeOverlayManager);
 		if (cmpRangeOverlayManager)
 			cmpRangeOverlayManager.SetEnabled(true, this.enabledVisualRangeOverlayTypes);
Index: binaries/data/mods/public/simulation/components/Settlement.js
===================================================================
--- binaries/data/mods/public/simulation/components/Settlement.js
+++ binaries/data/mods/public/simulation/components/Settlement.js
@@ -1,15 +0,0 @@
-function Settlement() {}
-
-Settlement.prototype.Schema =
-	"<empty/>";
-
-Engine.RegisterComponentType(IID_Settlement, "Settlement", Settlement);
-
-/*
- * TODO: the vague plan is that this should keep track of who currently owns the settlement,
- * and some other code can detect this (or get notified of changes) when it needs to.
- * A civcenter's BuildRestrictions component will see that it's being built on this settlement,
- * call MoveOutOfWorld on us (so we're invisible and only the building is visible/selectable),
- * tell us that its player owns us, and move us back into our original position when the building
- * is destroyed. Don't know if that's a sensible plan, though.
- */
Index: binaries/data/mods/public/simulation/components/interfaces/BuildSlot.js
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/components/interfaces/BuildSlot.js
@@ -0,0 +1 @@
+Engine.RegisterInterface("BuildSlot");
Index: binaries/data/mods/public/simulation/components/tests/test_BuildSlot.js
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/components/tests/test_BuildSlot.js
@@ -0,0 +1,13 @@
+Engine.LoadComponentScript("interfaces/BuildSlot.js");
+Engine.LoadComponentScript("BuildSlot.js");
+
+const buildSlotId = 1;
+const buildingId = 2;
+
+let cmpBuildSlot = ConstructComponent(buildSlotId, "BuildSlot", {
+	"HideUponUse": "false"
+});
+
+TS_ASSERT_UNEVAL_EQUALS(cmpBuildSlot.GetOccupant(), INVALID_ENTITY);
+TS_ASSERT_UNEVAL_EQUALS(cmpBuildSlot.InitConstruction(buildingId), true);
+TS_ASSERT_UNEVAL_EQUALS(cmpBuildSlot.GetOccupant(), buildingId);
Index: binaries/data/mods/public/simulation/helpers/Commands.js
===================================================================
--- binaries/data/mods/public/simulation/helpers/Commands.js
+++ binaries/data/mods/public/simulation/helpers/Commands.js
@@ -1136,6 +1136,13 @@
 	if (cmpVisual && cmd.actorSeed !== undefined)
 		cmpVisual.SetActorSeed(cmd.actorSeed);
 
+	if (cmd.snapEntity)
+	{
+		let cmpBuildSlot = Engine.QueryInterface(cmd.snapEntity, IID_BuildSlot);
+		if (cmpBuildSlot)
+			cmpBuildSlot.InitConstruction(ent);
+	}
+
 	// Initialise the foundation
 	var cmpFoundation = Engine.QueryInterface(ent, IID_Foundation);
 	cmpFoundation.InitialiseConstruction(player, cmd.template);
Index: binaries/data/mods/public/simulation/templates/template_socket.xml
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/templates/template_socket.xml
@@ -0,0 +1,93 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Entity>
+  <AIProxy/>
+  <BuildRestrictions>
+    <PlacementType>land</PlacementType>
+    <Territory>own</Territory>
+    <Category>special</Category>
+  </BuildRestrictions>
+  <BuildSlot>
+    <HideUponUse>true</HideUponUse>
+  </BuildSlot>
+  <Capturable>
+    <CapturePoints>500</CapturePoints>
+    <RegenRate>0.5</RegenRate>
+    <GarrisonRegenRate>5.0</GarrisonRegenRate>
+  </Capturable>
+  <Cost>
+    <Population>0</Population>
+    <PopulationBonus>0</PopulationBonus>
+    <BuildTime>1</BuildTime>
+    <Resources>
+      <food>0</food>
+      <wood>0</wood>
+      <stone>0</stone>
+      <metal>0</metal>
+    </Resources>
+  </Cost>
+  <Health>
+    <Max>10</Max>
+    <DamageVariants>
+      <lightdamage>0.85</lightdamage>
+      <mediumdamage>0.65</mediumdamage>
+      <heavydamage>0.35</heavydamage>
+    </DamageVariants>
+    <DeathType>corpse</DeathType>
+    <RegenRate>0</RegenRate>
+    <IdleRegenRate>0</IdleRegenRate>
+    <Unhealable>true</Unhealable>
+  </Health>
+  <Identity>
+    <Civ>gaia</Civ>
+    <GenericName>Socket</GenericName>
+    <Classes datatype="tokens">socket_house</Classes>
+    <Undeletable>true</Undeletable>
+  </Identity>
+  <Obstruction>
+    <Active>true</Active>
+    <BlockMovement>true</BlockMovement>
+    <BlockPathfinding>true</BlockPathfinding>
+    <BlockFoundation>true</BlockFoundation>
+    <BlockConstruction>false</BlockConstruction>
+    <DisableBlockMovement>false</DisableBlockMovement>
+    <DisableBlockPathfinding>false</DisableBlockPathfinding>
+    <DeleteUponConstruction>false</DeleteUponConstruction>
+    <Static width="11.0" depth="11.0"/>
+  </Obstruction>
+  <OverlayRenderer/>
+  <Ownership/>
+  <Position>
+    <Altitude>0</Altitude>
+    <Anchor>upright</Anchor>
+    <Floating>false</Floating>
+    <FloatDepth>0.0</FloatDepth>
+    <TurnRate>6.0</TurnRate>
+  </Position>
+  <Selectable>
+    <Overlay>
+      <Outline>
+        <LineTexture>outline_border.png</LineTexture>
+        <LineTextureMask>outline_border_mask.png</LineTextureMask>
+        <LineThickness>0.4</LineThickness>
+      </Outline>
+    </Overlay>
+  </Selectable>
+  <StatusBars>
+    <BarWidth>6.0</BarWidth>
+    <BarHeight>0.6</BarHeight>
+    <HeightOffset>12.0</HeightOffset>
+  </StatusBars>
+  <Visibility>
+    <RetainInFog>true</RetainInFog>
+    <AlwaysVisible>false</AlwaysVisible>
+    <Corpse>false</Corpse>
+    <Preview>false</Preview>
+  </Visibility>
+  <VisualActor>
+    <ConstructionPreview/>
+    <SilhouetteDisplay>false</SilhouetteDisplay>
+    <SilhouetteOccluder>true</SilhouetteOccluder>
+    <VisibleInAtlasOnly>false</VisibleInAtlasOnly>
+    <Actor>structures/fndn_3x3.xml</Actor>
+  </VisualActor>
+</Entity>
Index: binaries/data/mods/public/simulation/templates/template_structure_civic_house.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_structure_civic_house.xml
+++ binaries/data/mods/public/simulation/templates/template_structure_civic_house.xml
@@ -1,7 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Entity parent="template_structure_civic">
   <BuildRestrictions>
+    <PlacementType>socket</PlacementType>
     <Category>House</Category>
+    <Sockets datatype="tokens">socket_house</Sockets>
   </BuildRestrictions>
   <Capturable>
     <CapturePoints>300</CapturePoints>
Index: binaries/data/mods/public/simulation/templates/template_unit_infantry.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_unit_infantry.xml
+++ binaries/data/mods/public/simulation/templates/template_unit_infantry.xml
@@ -24,6 +24,7 @@
   <Builder>
     <Rate>1.0</Rate>
     <Entities datatype="tokens">
+      template_socket
       structures/{civ}_civil_centre
       structures/{civ}_crannog
       structures/{civ}_military_colony