I would like to make a book cover on top of a 6x9 industry standard (Lightning Source Publishing) three piece (front cover, spine, and back cover) template. Like most people I put background layers on top of the template. And then letters and images on top of the back ground layers. Now, how do I cut a hole through the background on the back cover to expose the bar code? Am I clear?

Lightning Source Publishing sends you a template with your ISBN number printed in black on the bottom of the back cover. How do I cut through the background layer to expose the ISBN number on the template to view?

Use a clip http://en.flossmanuals.net/Inkscape/ClipAndMask
http://tavmjong.free.fr/INKSCAPE/MANUAL ... pping.html

Let me ask the question from another direction. ....

Assume I have a background layer resting on top of the back cover space of my book cover template. Suppose I use the bezier tool to construct a rectangle on top of the background layer. What commands do I have to issue to make the substance of the rectangle transparent so as to reveal the bar code on the template layer beneath the background layer I put on top of the template?

Mask it
Colors to use in your mask Directly above your grouped cover art

Make One Square/Rectangul no stroke Color it WHITE.. make sure it is larger than your art work.
Make another Square no stroke Color is BLACK make it the size of the area you want cut out to see the barcode.
Group the WHITE and BLACK rectanguls..this will be your MASK
Select your artwork and your MASK and the select >Object >Mask.. >Set done

Yes that's the trick, you have to have an object that is larger than your artwork to show parts around the hole. Then use a group as vwanweb mentioned or select the big and small rectangle and do Path > Difference to get a square donut like shape and use it to clip or mask your drawing.