A carpet knife is essential for any job involving carpet, and it's good for other DIY projects as well. Here's what you need to know.

Use a utility knife or drywall saw to cut a patch of drywall to size for the opening. It needs to fit like a puzzle piece. Always double-check your measurements. A snug fit is important.

When you're hanging drywall, there's more at stake ... When you're scoring with a utility knife, use only enough pressure to ...