Thanks again for replying. Sorry it has taken a while for me to get back to you but we have been entertaining two granddaughters for a couple of days. I now need a holiday.
I can now understand what you were proposing. From your image I made the erroneous assumption that you had e-snapped to the top plane of the the box. Silly me!
I have attached an image of what I was trying to do in TC. It isn't perfect, but was good enough for grandson's birthday card. I used CorelDraw for this.
Again, thanks for your time and help.
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