If by conrete you mean concrete, it is put in the backyard the same way as it is put in the front yard. However, in some cases, you cant access the backyard from the street therefore an concrete pump is needed. The concrete truck will empty it's load into a hopper on the back of the concrete pump. Then it gets pumped through a pipe which is held up by a remote controlled boom, allowing concrete to be pumped over fences, houses etc...
There is no monster bunker on backyard monsters!
Yes.Yes.Yes.Yes.Yes.Yes.Yes.Yes.Yes.
To put igloo items in your backyard on Club Penguin you will first need to select the type of igloo you want. You can then select the accessories and items you want to include and place them in the backyard.
concrete is a mixture
You can't place items in your backyard. The only things that can go in your backyard are your puffles. Whilst your puffles are in your backyard, their stats (energy, health, etc.) all stay the same.
Put them in your bunker.
swingset, fence, pool, sandbox
If it's YOUR backyard, then yes.
Fill it with soil and put grass seed on it
If you own the land, you can put them to use or sell them for their market value.
I put it there to trick you, and I believe it has worked.
Generally a cage. But i put a double-wide in the backyard for mine....