Alter Item to Gargoyle

[ReApEr]

Is there anyway to make the Alter Item button on Tools work on Custom armor?

I mean I know I can add

[Alterable(typeof(DefTailoring), typeof(GargishLeatherArms))]

To Custom Arms say but why do i have to when LeatherArms already has it that in it?

using Server.Engines.Craft;

namespace Server.Items
{
    [Alterable(typeof(DefTailoring), typeof(GargishLeatherArms))] // << Why do i need this when LeatherArms already has this?
    public class FireArms : LeatherArms