I'll be embedding them in the concrete head of a fireplace I'm building at the moment which is similar to one I did a few years ago. One end of each coupler will be open and flush with the surface of the finished concrete whilst the other embedded end will have had a bolt welded in it to stop the wet concrete from passing through the coupler and blocking it. To hold the coupler\bolt fixtures securely in place whilst the concrete was being poured I drilled holes in the shutter and used another bolt screwed through the shutter into the open end of each coupler. I'll take a few photos to document the process when the time comes. Here's a photo of the new fireplace.
The eye embedded in the lower part of the right hand pier is from the original fireplace and was used to hang the crane from. Also note the rectangular hole in the back wall, this is for the heating pipes from the stove. There is a matching hole at the back of the middle pier.