It might be too confusing to explain on here or it might just be rubbish, but I'll tell you all anyway as I'm bored...
They are in a big task room and it's split up into 6 sections. The sections are just tiny rooms with two doors either side that link on to the next section so basically it's just one big rectangle room with doors separating them so HMs can run into each of them.
Housemates will all have their own individual section and there will be a poster of them in their section so everyone knows it's theirs. HMs will start with start with say two blocks in their section and will have to try put the blocks in other people's sections.
The aim is to have as few as possible blocks in your section. The two/three HMs with the most blocks in their section at the end will be up for eviction.
Then when it's finished Big Brother can show a recording of the task and HMs can see who tried to get them out by putting blocks in their section.
Sorry if it's confusing or crap but like I said I'm really bored, nothing is on TV so I thought I'd share this

Apologies for using the word 'section' too much