Illustrator CS6 how to question

Hello I just started playing with a die cutting machine and am trying to create pop up text or text that is cut along the edge of the page and I can't figure out how to create an open end in the text so it won't be cut. I have tried adding a white box over the ends that i don't want to cut but when I export the file to the cutting software (sure cuts alot) I get the outline of the box in the .svg file. Does anyone have any ideas how to make this work. I don't know if I've explained this well but I attached an example of what I'm hoping to do.

Thanks
Jason

Awesome that did it!! thank you so much I knew I was missing something simple.

Thanks
Jason

Ok maybe not. That did the trick visually but when I save the file as a .svg it keeps the masking box as part of the file and closes up the ends. Is there a way to remove a line segment from text without changing the shape. I've tried editing the mask but it still remains after I save it. I've also tried everything in the Pathfinder menu with no success.

Thanks
Jason

Thanks, I guess I wasn't looking at it right. I come from a printing background and have been approaching it from that end I need to learn to think cutting not printing and focus on the negative spaces.

Thanks for all the help
Jason