No junction box. it's a wall unit air condition, it slides right in the
hole.
You say: apply concrete to top of hole, then put wood to keep it from
falling down..if it hasn't fallen down before I put the wood I don't need to
put the wood.
req
"SteveBell" <respond@online.newsgroup.invalid> wrote in message
> news:xn0fwnl9egpn6s000@news.motzarella.org...
> >
[quoted text clipped - 23 lines]
> keep it from falling down..if it hasn't fallen down before I put the
> wood I don't need to put the wood.
I'm sorry. I thought you were making an opening for an AC (alternating
current) junction box opening smaller. Chuckles all round. :-) In that
case, you would have forced the concrete into the top of the hole, then
put in a piece of wood to keep it from slowly sagging. The small amount
of very thick concrete would have stayed in place long enough to get
some support under it.
On topic:
Build a wooden form. Somehow (how I don't know) get the concrete into
the form on top of the wood. This sounds difficult.
I suggest you just insulate the inside of your concrete blocks with
expandable foam, then add wood trim to make the opening the right size
for your air conditioner. Finish off with some door casing to hide the
edges of the opening.

Signature
Steve Bell
New Life Home Improvement
Arlington, TX
Erik Dillenkofer - 21 Oct 2008 10:22 GMT
How about installing a form board across the top of the hole, drilling holes
into the block "voids", pouring concrete into those holes, then patching the
holes?
> "SteveBell" <respond@online.newsgroup.invalid> wrote in message
>> news:xn0fwnl9egpn6s000@news.motzarella.org...
[quoted text clipped - 40 lines]
> for your air conditioner. Finish off with some door casing to hide the
> edges of the opening.
SteveBell - 21 Oct 2008 13:55 GMT
> >"SteveBell" <respond@online.newsgroup.invalid> wrote in message
> > > news:xn0fwnl9egpn6s000@news.motzarella.org...
[quoted text clipped - 44 lines]
> drilling holes into the block "voids", pouring concrete into those
> holes, then patching the holes?
Sounds like a plan to me.

Signature
Steve Bell
New Life Home Improvement
Arlington, TX
reqluq - 21 Oct 2008 19:34 GMT
Excellent!
req
> How about installing a form board across the top of the hole, drilling
> holes into the block "voids", pouring concrete into those holes, then
[quoted text clipped - 44 lines]
>> for your air conditioner. Finish off with some door casing to hide the
>> edges of the opening.
PeterD - 21 Oct 2008 14:33 GMT
>"SteveBell" <respond@online.newsgroup.invalid> wrote in message
>> news:xn0fwnl9egpn6s000@news.motzarella.org...
[quoted text clipped - 40 lines]
>for your air conditioner. Finish off with some door casing to hide the
>edges of the opening.
Another way would be to frame the bottom piece, and one side. Then
fill that space with a very dry mix, and slap on the other side when
the space is filled. A couple of big C clamps could be used to hold
the side on as the mix set.