I have a series of blocks at the base of my mast for ... I need to add an additional for the boom vang. Every block that is there is in use, so I have to add another. Do they lock in some way or do I have to have the mast stepped and pull the plate? No, I have not gone to the store and looked at the blocks yet, i am trying to see how deep the """" I will be getting myself into before I bother having the dealer do it.