Index: src/ai/api/ai_sign.hpp.sq
===================================================================
--- src/ai/api/ai_sign.hpp.sq	(revision 12185)
+++ src/ai/api/ai_sign.hpp.sq	(working copy)
@@ -15,14 +15,13 @@
 	SQAISign.AddConstructor<void (AISign::*)(), 1>(engine, "x");
 
 	SQAISign.DefSQStaticMethod(engine, &AISign::GetClassName, "GetClassName", 1, "x");
+	SQAISign.DefSQStaticMethod(engine, &AISign::GetMaxSignID, "GetMaxSignID", 1, "x");
+	SQAISign.DefSQStaticMethod(engine, &AISign::GetSignCount, "GetSignCount", 1, "x");
 	SQAISign.DefSQStaticMethod(engine, &AISign::IsValidSign,  "IsValidSign",  2, "xi");
+	SQAISign.DefSQStaticMethod(engine, &AISign::GetText,      "GetText",      2, "xi");
+	SQAISign.DefSQStaticMethod(engine, &AISign::GetLocation,  "GetLocation",  2, "xi");
+	SQAISign.DefSQStaticMethod(engine, &AISign::RemoveSign,   "RemoveSign",   2, "xi");
+	SQAISign.DefSQStaticMethod(engine, &AISign::BuildSign,    "BuildSign",    3, "xis");
 
-	SQAISign.DefSQMethod(engine, &AISign::GetMaxSignID, "GetMaxSignID", 1, "x");
-	SQAISign.DefSQMethod(engine, &AISign::GetSignCount, "GetSignCount", 1, "x");
-	SQAISign.DefSQMethod(engine, &AISign::GetText,      "GetText",      2, "xi");
-	SQAISign.DefSQMethod(engine, &AISign::GetLocation,  "GetLocation",  2, "xi");
-	SQAISign.DefSQMethod(engine, &AISign::RemoveSign,   "RemoveSign",   2, "xi");
-	SQAISign.DefSQMethod(engine, &AISign::BuildSign,    "BuildSign",    3, "xis");
-
 	SQAISign.PostRegister(engine);
 }
Index: src/ai/api/ai_sign.hpp
===================================================================
--- src/ai/api/ai_sign.hpp	(revision 12185)
+++ src/ai/api/ai_sign.hpp	(working copy)
@@ -22,7 +22,7 @@
 	 * @return the maximum sign index.
 	 * @post return value is always non-negative.
 	 */
-	SignID GetMaxSignID();
+	static SignID GetMaxSignID();
 
 	/**
 	 * Gets the number of signs. This is different than GetMaxSignID()
@@ -30,7 +30,7 @@
 	 * @return the number of signs.
 	 * @post return value is always non-negative.
 	 */
-	int32 GetSignCount();
+	static int32 GetSignCount();
 
 	/**
 	 * Checks whether the given sign index is valid.
@@ -46,7 +46,7 @@
 	 * @return the text on the sign.
 	 * @note the returned name must be free'd (C++ only).
 	 */
-	char *GetText(SignID sign_id);
+	static char *GetText(SignID sign_id);
 
 	/**
 	 * Gets the location of the sign.
@@ -55,7 +55,7 @@
 	 * @return the location of the sign.
 	 * @post return value is always positive and below AIMap::GetMapSize().
 	 */
-	TileIndex GetLocation(SignID sign_id);
+	static TileIndex GetLocation(SignID sign_id);
 
 	/**
 	 * Removes a sign from the map.
@@ -63,7 +63,7 @@
 	 * @pre sign_id has to be valid (use IsValidSign()).
 	 * @return true if and only if the sign has been removed.
 	 */
-	bool RemoveSign(SignID sign_id);
+	static bool RemoveSign(SignID sign_id);
 
 	/**
 	 * Builds a sign on the map.
@@ -75,7 +75,7 @@
 	 *   In test-mode it returns 0 if successful, or any other value to indicate
 	 *   failure.
 	 */
-	SignID BuildSign(TileIndex location, const char *text);
+	static SignID BuildSign(TileIndex location, const char *text);
 };
 
 #endif /* AI_SIGN_HPP */
Index: src/ai/api/ai_sign.cpp
===================================================================
--- src/ai/api/ai_sign.cpp	(revision 12185)
+++ src/ai/api/ai_sign.cpp	(working copy)
@@ -48,7 +48,7 @@
 bool AISign::RemoveSign(SignID sign_id)
 {
 	_cmd_text = "";
-	return this->DoCommand(0, sign_id, 0, CMD_RENAME_SIGN);
+	return DoCommand(0, sign_id, 0, CMD_RENAME_SIGN);
 }
 
 SignID AISign::BuildSign(TileIndex location, const char *text)
@@ -58,14 +58,14 @@
 	/* Reset the internal NewSignID in case we are in TestMode */
 	AIObject::SetNewSignID(0);
 
-	bool ret = this->DoCommand(location, 0, 0, CMD_PLACE_SIGN);
+	bool ret = DoCommand(location, 0, 0, CMD_PLACE_SIGN);
 	if (!ret) return INVALID_SIGN;
 
 	SignID new_sign_id = AIObject::GetNewSignID();
 	_cmd_text = text;
-	ret = this->DoCommand(0, new_sign_id, 0, CMD_RENAME_SIGN);
+	ret = DoCommand(0, new_sign_id, 0, CMD_RENAME_SIGN);
 	if (!ret) {
-		this->RemoveSign(new_sign_id);
+		RemoveSign(new_sign_id);
 		return INVALID_SIGN;
 	}
 	return new_sign_id;