Because you can unlock items, I assume you can lock them and that this is a server side state. If so then how do you go about locking an item?

I am trying to get, for example, the toolcupboard to be a locked blueprint, so that it does not show up in the craft menu unless you "unlock" it or search for it explicitly.

I have tried the following, and while it stops me from crafting the item, it still shows up in my craft menu

bp.userCraftable = false;
bp.defaultBlueprint = false;
bp.isResearchable = false;​

TLDR; it's not possible for already unlocked items.

It appears some of the initial items are unlocked clientside since the unlockedlist is empty. So you can only unlock items that are alraedy locked clientside with an RPC call, but you can not lock item that are unlocked by default since there is no "locked" list like there is an "unlocked" list which you can RPC send to the client.

            var playerInfo = player.PersistantPlayerInfo;
            Puts("count: " + playerInfo.unlockedItems.Count);​

The following code proves this because its count value is 0, proving there are no default unlocks in this list, and it is just clientside.