interface builder red horizontal line

I have a xib file open, and I was playing around with it one day and I must have pressed something. Now there is a red horizontal line in the xib file, and when I put the mouse over it, the cursor turns into a double arrow that you can drag up and down. If I drag it, it creates anot开发者_如何转开发her red horizontal line. What does this line do? How do I get rid of it?

Thanks!

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Sounds like a custom Horizontal Guide (see Layout menu) which can be used to help line up controls in the UI. It appears only in the IB design window (it doesn't become part of the UI).

To remove it, drag it off the top or bottom of the window and it will disappear in a puff of smoke.