See the question and my original answer on StackOverflow

Other languages do support it, but you cannot use an array of strings from VBScript (internally and in the type library it will be represented as a SAFEARRAY of BSTR).

It only support an array of objects, but you can also use the old ArrayList .NET class (which also allows for each type enumeration), for example in C#:

public interface IComMethods
    ArrayList Interlockings { get; }
    object[] InterlockingsAsObjects { get; }

public class MyClass: IComMethods
    public ArrayList Interlockings => new ArrayList(new string[] { "abc", "def" });
    public object[] InterlockingsAsObjects => new object[] { "abc", "def" };

And in VBScript:

set x = CreateObject("MyClassLibrary.MyClass")

' ArrayList
WScript.Echo "Count " & x.Interlockings.Count

for each il in x.Interlockings
    WScript.Echo il

WScript.Echo x.Interlockings.Item(1) ' def

' array of objects
ar = x.InterlockingsAsObjects
WScript.Echo "Count " & ubound(ar) - lbound(ar) + 1

for i = lbound(ar) to ubound(ar)
    WScript.Echo ar(i)

WScript.Echo ar(1) ' def

Another trick is to declare a COM interface as VBScript expects, but implement it privately so it looks better to .NET callers, something like this:

public class MyClass : IComMethods
    // better for .NET clients
    public string[] Interlockings => new string[] { "abc", "def" };

    // explicit implementation
    object[] IComMethods.Interlockings => Interlockings.ToArray<object>();

public interface IComMethods
    object[] Interlockings { get; }

Obviously, you can do the same with ArrayList instead of object[].