>Is it possible? I can't find a setting. Tried making rectangles as 'boxes', and placing the fields in them, but that makes a gap print between the 'lines' if you centralize the fields height in the rectangles.
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>Thanks.

My excel does not print any lines? Do you like to add up a grid like structure? There is the line report stuff. Just place the lines to appropriate positions and manipulate as along as it fits to your needs

hint:
one horizontal line per detail is enough. place it at bottom of detail band. similar structure on header / caption

You need to learn the correct placement by moving and resizing. I could tell you, but this is a pain, and it's not that tricky.
Turn status bar (tools options) and on the same form reports / show position in status bar. You will see the boundaries of the item(s) selected. Ah and I think pixels are better then any other unit on this ...