CSG Subtract greyed out when I need it

I am now on the "Breakthrough I" tutorial in the WED Editor tutorial from the GS7 downloads page.

I created two small blocks, one to fit on the wall as an archway doorway entrance, and another to serve as a cutting tool to cut the first block in the shape of the archway. However, every time I finish cutting the first block in the archway shape I want it, I place it in the wall directly in front of where the archway in the house starts, and when I am ready to use Edit/CSG Subtract option, it is continually grayed out.

I found this in the tutorial:

"If CSG Subtract is greyed out, you've probably made a little mistake when shaping the block. Try again and make sure not to accidentally cut a 'notch' in your arch cutting tool. Otherwise it will automatically divided into a group - you'll see this in the editor - and then can't be used anymore for cutting doorways. Your wall however might be divided a bit, but so long as we don't go moving individual parts of it around we'll be okay. In any case, we won't be using the wall as a cutter."

I am confused as to what this is saying. How am I able to "cut a 'notch' in my arch cutting tool". I thought it is only able to cut the first block. How can the arch cutting tool be able to cut itself?

CSG subtract only works when the cutting tool is a single block (not a group)
You may be using a group as a cutting tool. Try isolating the block you're using as a cutter.

Hi!

Also

you do not put it in front
You place it in the wall. It sticks out on both sides.

To my knowledge, I did not do anything to the cutting block to make it a group. I simply cut the corners of the doorway block like the tutorial told me to do, and every time the CSG Subtract is grayed out when I place my newly shaped doorway into the wall. I just did it again today, and I got the same results. There must be something I am doing wrong, but I cannot figure out what just yet.

I thought the cutting block I created remains a block while shaping the doorway block, instead of turning into a group. Is there perhaps something I am doing wrong that would somehow change the cutting block I created into a group, while in the process of cutting (shaping) the doorway block?

Thank you. I did do that, and the CSG Subtract is still grayed out.

1.) Use the EDIT button!

2.) As mentioned above you cannot use groups with CSG Subtract. When you form your block to a "newly shaped doorway", it will become a group of blocks.
Instead, better stay with a simple block, cut out a rectangular shape and then add smaller blocks manually to achieve the desired effect using Edge Move. In general this will lead to better results than using CSG Subtract.

I do know that the edges I cut with the cutting block are not perfectly lined up with the archway lines. They are very close, but not perfectly in line. I do not know if that has anything to do with why the CSG Subtract is grayed out, but I thought I would mention it.

Did you read my post at all?

Thank you Superku. It looks like it worked. I really appreciate it. :-)