Delete (old) blocks

[106miles]

Hello, we use The modul designer with vtiger 6.2.0. So we construct in the modul designer 5 blocks.But sometimes we have given the blocks new names and now we have following situation. The present blocks we work on the module maker actual version are the same you can see in the modul if you want to build up a new data. But when you using the posibility to work on the modul for example add a new custome field you will see all the old once blocks ( in our case 11 ) and you havent any possibilty to erase them How we can delete these old blocks ?