In the another display of passive aggressive behavior, I want to show you a trick you can use to prevent anyone from adding or deleting rows or columns by using a simple array formula.
I'm pretty sure I got this trick from Bob Umlas. Most Bob tricks, they are extremely cool, but I never seem to find situations where I can use them. But, maybe this trick will hit the spot for some of you.
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Step 1: Highlight the rows where you don't rows added or deleted.
Type =""
Press Shift+Ctrl+Enter to apply the array.

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Step 2: Highlight the columns where you don't rows added or deleted.
Type =""
Press Shift+Ctrl+Enter to apply the array.

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Step 3: Hide the array formulas along with anything else you don't want your users to see.
When your users try to add or delete a column or row in the protected area, they'll get a face full of error message.

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I think this would be useful if you didn't want apply sheet protection but still wanted to prevent structural changes. Although – I can't think of any reason why you would stay away from sheet protection.
What do you think?