Right back to the review,
Having reset the blades in the other end !
Holding the tool in one hand fully open like a hand of cards, I left one bolt slightly loose to enable the card like look. I started to pop the blades in place. Not the easiest of things to do as they can fall out , but each time once in you have to close that leaf. Once done the with the whole thing now closed up the blot in replaced and screwed in to the captive nut.
All in place and ready to mark .

Running the blade against a rule gives this ,
By this time I had marked out the width of the bricks, using a wooden marker, after all the struggle with the setting up no way was I going to remove some of the blades !
Then using a thin filer knife blade I made the lines wider for the mortar

Do think Jim's idea of the plastic card worth doing.
The width of the brick was just done with the scaple, still think the width between the lines is too little , so didn't use my home made tool or the dental one.
Don't think any of us would bother with this, home made ones would be far better OR the single line with a ruler .Worth a try as you never know.
Thanks goes to MIKE " IS IT ME " for sending it to me to try.
Thanks for all the comments.
John.